UC-NRLF 


35    715 


GIFT   OF 

PROF.  W.B.  RISING 


SPECTRUM  ANALYSIS. 


ELEMENTS 


OF 


MODERN  CHEMISTRY. 


BY   ADOLPHE   WURTZ, 

MEMBER    OF    THE     INSTITUTE,    HONORARY    DEAN    AND     PROFESSOR    OF 

CHEMISTRY  OF  THE  FACULTY  OF  MEDICINE  OF  PARIS,  MEMBER 

OF    THE    ACADEMY   OF    MEDICINE,    ETC. 


TRANSLATED  AND  EDITED,  WITH  THE  APPROBATION  OF  THE  AUTHOR, 
FROM  THE  FOURTH  FRENCH  EDITION, 


BY    WM.    H.    GREENE,    M.D., 

DEMONSTRATOR    OF    CHEMISTRY    IN   THE    MEDICAL    DEPARTMENT   OK    THE 

UNIVERSITY    OF    PENNSYLVANIA,    MEMBER    OF    THE    AMERICAN 

PHILOSOPHICAL  SOCIETY,  OF  THE  CHEMICAL  SOCIETIES 

OF    PARIS    AND    BERLIN,    ETC. 


WITH    ONE    HUNDRED -\ND    THIKTY-TW,0  JLLJJS^T RATIONS 


LONDON  AND  PHILADELPHIA: 

J.   B.   LIPPINCOTT     &    CO. 

1880. 

(ALL   RIGHTS  RESERVED.) 


Copyright,  1879,  by  J.  B.  LIPPINCOTT  &  Co. 


AUTHOR'S   PREFACE, 


THIS  book  is  translated  from  the  fourth  French  edition  by 
my  pupil  and  friend,  M.  Greene,  whose  perfect  familiarity  with 
the  French  language  and  thorough  competence,  at  the  same 
time,  in  chemistry  I  have  had  occasion  to  appreciate.  The 
translation  is,  then,  a  faithful,  or  even  improved,  representation 
of  the  original  work,  in  which  he  will  certainly  have  detected 
and  corrected  some  faults. 

The  French  editions  succeed  each  other  rapidly,  showing 
that  this  little  book  responds  to  an  educational  need. 

It  has  been  the  endeavor  to  keep  it  up  with  the  current  of 
the  latest  discoveries,  and  in  it  to  condense  a  considerable 
number  of  exact  and  well-selected  facts,  without  banishing  the 
theory  which  binds  them  together.  Thus,  the  origin  and  foun- 
dation of  the  atomic  theory  have  been  given,  as  far  as  possible, 
in  historical  order.  The  notions  concerning  atomicity,  so  im- 
portant for  the  appreciation  of  the  structure  of  combinations 
and  for  the  interpretation  of  chemical  reactions,  are  presented 
in  an  elementary  form. 

The  reader  will  remark  that  the  history  of  the  metalloids 
is  relatively  more  developed  than  the  remainder  of  the  book. 
Indeed,  this  is  the  fundamental  part  of  chemistry,  and  a  fa- 
miliar knowledge  of  it  is  indispensable  to  the  fruitful  study  of 
the  metals  and  of  organic  chemistry.  It  is  also  the  most  at- 
tractive portion  for  beginners,  for  it  is  the  most  easily  under- 
stood. 

Immediately  on  entering  the  immense  domain  of  organic 

iii 

237376 


1V  AUTHOR'S  PREFACE. 

chemistry,  we  find  the  facts  overwhelmingly  numerous  and 
complicated.  Among  all  these  facts  a  severe  and  careful 
choice  has  been  made,  the  historical  importance  and  the  theo- 
retical and  practical  interest  of  the  compounds  described  being 
borne  in  mind.  In  this  respect  many  additions  have  been 
made  to  the  third  French  edition.  Thus,  the  question  of 
isomerism,  upon  which  the  theory  of  atomicity  has  thrown  so 
much  light,  has  been  treated  in  a  more  thorough  manner. 
The  chapter  on  the  aromatic  compounds  has  been  considerably 
augmented. 

The  author  hopes  that  these  "  Elementary  Lessons"  will  be 
well  received  by  the  new  public  to  whom  they  are  presented, 
and  that  they  will  contribute  to  render  attractive  and  diffuse 
the  knowledge  of  the  science  to  which  he  has  devoted  his  life. 

ADOLPHE   WURTZ. 

PARIS,  November  20,  1878. 


TRANSLATOR'S  PREFACE. 


IT  is  a  privilege  to  be  able  to  bring  before  the  English-read- 
ing public  a  work  by  one  who  has  justly  won  the  reputation  of 
being  the  most  able  thinker  and  perspicuous  teacher  of  France. 
M.  Wurtz  is  the  acknowledged  leader  of  modern  chemical 
philosophy,  and  his  labors  have  firmly  established  many  of 
the  views  which  long  remained  unaccepted  by  the  majority 
of  chemists,  but  which  are  now  regarded  as  essential  to  the 
science. 

This  book  is  therefore  a  brief  but  accurate  embodiment  of 
modern  chemical  ideas,  arranged  in  such  a  form  that  the  most 
difficult  principles  are  acquired  gradually  in  the  course  of  the 
descriptions. 

While  the  original  has  been  carefully  followed,  a  few  slight 
changes  and  additions  have  been  made.  Some  mineral  sources 
not  given  in  the  French  edition  have  been  introduced,  and  a 
few  processes  to  which  greater  attention  is  generally  paid  in 
English  works  have  been  more  fully  developed. 

WM.  H.  GREENE. 


TABLE  OF  CONTENTS. 


PAGE 

INTRODUCTION — DISTINCTION  BETWEEN  CHEMICAL  AND  PHYSICAL  AC- 
TION  7-9 

DEFINITION  OP  CHEMISTRY 10 

AFFINITY — MOLECULES — ATOMS 11-13 

DECOMPOSITION — DOUBLE  DECOMPOSITION 17-20 

LAW  OF  DEFINITE  PROPORTIONS — EQUIVALENTS — MULTIPLE  PROPOR- 
TIONS         •        •        .         21-26 

HYPOTHESIS  OF  ATOMS •        •        .26 

GAY-LUSSAC'S  LAW — ATOMIC  THEORY 27 

AMPERE'S  LAW — AVOGADRO'S  LAW 30-32 

LAW  OF  SPECIFIC  HEATS 34 

LAW  OF  ISOMORPHISM .        .        .37 

NOMENCLATURE  AND  NOTATION 37 

Hydrogen 48 

Oxygen 54 

Ozone .         .         . 59 

Air 63 

Water 70 

Mineral  Waters 82 

Sulphur  and  Compounds    ........        88-111 

Selenium  and  Tellurium Ill 

Chlorine  and  Compounds 112-127 

Bromine  and  Compounds    ........      127-130 

Iodine  and  Compounds       ........      130-136 

ANALOGIES  OF  CHLORINE  GROUP 136 

Fluorine— Hydrofluoric  Acid 136 

Nitrogen — Ammonia — Oxides  and  Acids  of  Nitrogen         .         .      138-161 
Phosphorus          ...........     161 

Arsenic 176 

Antimony  ............     185 

ANALOGIES  OF  NITROGEN  GROUP 190 

Boron 191 

Silicon 194 

Carbon 200 

vii 


Viii  TABLE   OP   CONTENTS. 

PAGE 

Compounds  of  Carbon  and  Hydrogen— Structure  of  Flame       .         .     217 
THEORY  OF  ATOMICITY 222 

General  Properties  of  Metals 231 

Alloys 236 

Oxides  and  Metallic  Hydrates 238-245 

Sulphides 245 

Chlorides .....        .         .     246 

Salts '.  .    -   «        •        •         .250 

Richter's  Laws   .        .        .         .        .         .        ..""...         .     253 

BERTHOLLET'S  LAWS 265 

Nitrates— Sulphates— Carbonates 271-277 

CLASSIFICATION  AND  ATOMICITY  OP  METALS 277 

Potassium 282 

Sodium 291 

Lithium 299 

Caesium  and  Rubidium— SPECTRUM  ANALYSIS 300 

Thallium — Barium .         .  302 

Strontium -'.,«-    •    .         .  304 

Calcium      .         .         .        *„„...       •„        » .  ; .:  .  305 

Magnesium          .         *         .      *  .         «         .         •        .         .        .'         .  310 

Aluminium          .         .        -»      •  V       .'       -.     :•".    c    .         .         .         .  313 
Clay  and  Pottery        .        ..       ..       V     r-*  -    V-"    •-       «,        .         .317 

Iron    .         .         .         .         *  .      i'       .         .       -,   "    ..-.         .  318 

Zinc    .         .         .        .,.'..      v       .        .        V        .        .         .  330 

Gallium       .         .         .-.'.'-*         .         .         .         »-       .         .         .  335 

Indium        . 336 

Cadmium    .         . 337 

Cobalt 338 

Nickel 340 

Manganese -.-       .        .         .         .        .  342 

Chromium  .        .     •  -i        .      ->*       •>.       .C      .       -»        •        .        .  346 

Bismuth 349 

Tin 352 

Lead .357 

Copper ......  368 

Mercury 375 

Silver 384 

Gold 391 

Platinum    .        .         .       v       ,        .        .        v.      .        .        .         .395 

ORGANIC  CHEMISTRY — TETRATOMICITY  OF  CARBON     ..'     .  .  ~     .        .  399 

HOMOLOGOUS  BODIES  .=..-*-•        .        .        .        .        .        .  405 

ELEMENTARY  ANALYSIS 406 

DETERMINATION  OF  MOLECULAR  WEIGHT   .        .        .        .        ,        .  410 

ISOMERISM — METAMERISM — POLYMERISM 412 

FUNCTIONS  OF  ORGANIC  COMPOUNDS    .        .        .        .        .        »        .  414 

Monatomic  Compounds .-»        .         .     415 

Polyatomic  Compounds  .        .        .        .        ...        .     426 

Cyanogen  Compounds .,        .     429 


TABLE   OF   CONTENTS.  IX 

PAGE 

Compounds  of  Carbon  Monoxide 438 

Monatomic  Alcohols  and  their  Derivatives         .....  444 

Saturated  Hydrocarbons 470 

Compound  Ammonias 479 

Organo-Metallic  Compounds       ........  486 

Volatile  Fatty  Acids  and  their  Derivatives         .....  488 

Polyatomic  Compounds  and  their  Derivatives 513 

Series  CnH2n 517 

Glycols 521 

Glycerin 529 

Polyatomic  Acids 536 

Uric  Acid  Series          ..........  559 

Higher  Alcohols          ..........  564 

Sugars  and  Starches 567 

Fermentation 577 

Glucosides  .         .         .         .         .         ..         .         .         .         .         .  586 

Aromatic  Compounds          .........  590 

Derivatives  of  Benzol 602-638 

Naphthalene 639 

Anthracene          ...........  640 

Natural  Alkaloids 643 

Albuminoid  Matters .  657 


ELEMENTS  OF  MODERN  CHEMISTRY. 


INTRODUCTION. 

THE  material  objects  surrounding  us  present  striking  and 
infinite  differences.  Sulphur  is  readily  distinguished  from 
charcoal,  rock-crystal  from  flint,  iron  from  copper,  water  from 
spirit  of  wine,  and  wood  from  ivory.  It  is  known  to  all  that 
these  bodies  differ  not  only  in  form,  density,  and  structure,  but 
also  in  their  proper  substance.  They  differ,  too,  in  the  changes 
through  which  they  pass  under  the  same  conditions.  When 
subjected  to  the  action  of  heat  they  receive  very  differently  the 
impression  of  that  force.  They  become  heated  more  or  less 
quickly,  and  transmit  the  heat  with  greater  or  less  rapidity 
throughout  their  own  substance.  A  short  bar  of  iron  cannot 
be  grasped  in  the  hand  by  one  extremity  if  the  other  be  heated 
to  redness ;  under  the  same  conditions  a  cylinder  of  charcoal 
may  be  handled  with  impunity.  Communicate  sufficient  heat  to 
water  and  it  is  converted  into  steam  ;  remove  heat  from  it,  and 
if  the  cooling  be  sufficient,  it  is  frozen  into  ice.  Spirit  of  wine 
cannot  be  congealed  by  the  most  intense  cold  known.  If  a 
magnet  be  placed  among  iron  filings  they  attach  themselves  in 
tufts  around  the  two  poles  ;  on  the  contrary,  copper  filings  are 
indifferent  to  the  magnetic  attraction. 

Rock-crystal  is  transparent  to  light ;  flint  is  opaque.  These 
two  bodies  are  unalterable  by  fire.  They  may  be  heated  to  red- 
ness in  a  furnace,  but  after  the  temperature  has  abated  they 
will  be  found  with  their  original  characters  unchanged.  It  is 
very  different  with  the  coal  which  we  burn  in  our  grates.  This 
body  disappears  during  the  combustion,  and  leaves  only  a  quan- 
tity of  ashes.  But  it  has  not  been  destroyed,  and  its  substance 
is  found  in  entirety  in  a  certain  gas  produced  by  the  combus- 
tion. Like  charcoal,  sulphur  is  combustible,  and  is  converted 
by  burning  into  a  gas,  the  suffocating  odor  of  which  is  well 
known. 

Neither  sulphur  nor  charcoal  undergo  any  alteration  when 


8  ELEMENTS    OF    MODERN    CHEMISTRY. 

exposed  to  damp  air  ;  it  is  not  the  same  with  iron.  In  a  moist 
atmosphere  this  metal  experiences  a  striking  and  lasting  change. 
Its  surface  becomes  covered  with  rust  and  is  no  longer  iron. 

In  the  forests,  the  leaves  which  fall  and  remain  upon  the 
moist  soil  are  slowly  consumed  and  disappear  in  the  course  of 
seasons. 

All  of  these  changes,  these  phenomena,  take  place  daily  be- 
fore our  eyes,  and  are  familiar  to  all  of  us.  On  comparison, 
striking  differences  are  discovered  between  them  :  some  are  but 
passing,  and  do  not  affect  the  proper  nature  of  the  body.  They 
are  the  results  of  forces  which  act  at  sensible  distances,  and 
which  leave  the  body  in  its  primitive  state  as  soon  as  their 
action  has  ceased.  A  piece  of  soft  iron  is  attracted  by  the 
magnet  before  contact  is  established,  and  when  under  the  mag- 
netic influence,  is  capable  of  attracting  other  soft  iron  in  its 
turn :  the  action  of  the  magnet  has  made  the  iron  itself  mag- 
netic, but  it  immediately  loses  this  property  when  the  magnet 
is  withdrawn  ;  and  further,  this  momentary  change  in  property 
has  brought  about  no  alteration  in  the  intimate  nature  of  the 
iron.  It  is  found  after  the  experiment  in  precisely  the  same 
condition  as  before. 

In  the  same  manner,  rock-crystal  undergoes  no  change  in  its 
specific  identity  by  the  passage  of  a  ray  of  light.  Withdraw 
from  the  vapor  of  water  the  heat  which  has  been  communi- 
cated to  it,  and  the  liquid  water  is  recovered  with  all  its  prop- 
erties. Restore  to  the  ice  the  heat  which  was  abstracted  in  its 
formation,  and  water  is  regenerated  as  before.  This  is  charac- 
teristic of  the  changes  produced  by  physical  forces.  Under 
the  influence  of  such  forces,  bodies  experience  modifications 
more  or  less  profound,  more  or  less  lasting,  but  which  never 
affect  their  specific  nature. 

But  the  iron  which  rusts  undergoes  a  complete  and  lasting 
change  in  its  properties  and  in  its  substance.  The  rust  is  no 
longer  iron,  and  vainly  would  it  be  sought  to  isolate  the  metal 
by  mechanical  means,  or  to  discover  its  presence  by  the  aid  of 
the  most  powerful  microscopes.  The  metal  has  disappeared  as 
such ;  it  has  undergone  a  complete  transformation ;  it  has  be- 
come another  body.  It  has  attracted  one  of  the  elements  of 
the  air,  oxygen,  and  has,  moreover,  fixed  to  itself  the  moisture 
of  the  atmosphere.  These  latter  bodies,  which  differ  from  iron 
in  substance,  have  intimately  united  with  the  metal  itself,  and 
the  result  of  this  union,  of  this  combination  as  it  is  called,  is 


INTRODUCTION. 


9 


a  new  body,  rust  or  hydrated  oxide  of  iron.  In  this  case  the 
alteration  is  profound,  the  change  is  lasting ;  the  specific  nature 
of  the  body  is  affected.  This  is  characteristic  of  chemical 
action. 

In  the  same  manner,  when  the  charcoal  and  the  sulphur  are 
burned  in  the  air?  they  attract  oxygen  and  combine  with  it, 
forming  two  new  bodies  that  are  called  carbonic  and  sul- 
phurous acids. 

These  phenomena  may  be  rendered  more  clear  by  simple  and 
well-known  experiments. 

Experiment  1. — A  globe  (Fig.  1)  is  filled  with  oxygen,  a 
gas  which  constitutes  one  of  the  elements  of  the  atmosphere, 
and  which  is  eminently  fitted  to  support  combustion  ;  into  it  is 
plunged  a  morsel  of  charcoal  lighted  at  one  end  ;  immediately 
the  coal  glows  with  a  brilliant  light,  the  combination  takes  place 
actively,  and  the  charcoal  is  rapidly  consumed.  But  presently 
the  light  becomes  paler,  the  combustion  ceases,  and  the  char- 
coal is  extinguished.  The  oxygen  is  now  nearly  or  quite  con- 


FIG.  1. 


FIG.  2. 


sumed,  and  the  globe  is  filled  with  another  gas  which  is  no 
longer  oxygen,  although  it  contains  that  oxygen.  It  contains 
also  the  matter  of  the  charcoal  which  has  disappeared,  and 
these  two  bodies  have  combined  to  form  a  new  body,  which  is 
carbonic  acid.  This  latter  will  not  support  combustion,  and 
further,  it  extinguishes  burning  bodies.  It  is  then  a  body 
having  entirely  new  properties,  and  is  formed  by  a  chemical 
action. 

Experiment  2. — Into  another  jar  filled  with  oxygen  (Fig.  2) 
is  plunged  a  spoon  containing  ignited  sulphur.     The  combus- 
A* 


10  ELEMENTS   OP   MODERN   CHEMISTRY. 

tion  takes  place  with  a  beautiful  blue  flame,  and  in  burning  in 
the  oxygen  with  so  much  energy,  the  sulphur  unites  with  the 
gas  and  forms  with  it  a  new  body,  which  is  called  anhydrous 
sulphurous  acid.  It  is  a  suffocating  gas,  which  extinguishes 
flame.  It  reddens,  and  afterwards  bleaches,  a  solution  of  blue 
litmus  poured  into  the  jar.  These  are  special  properties  which 
do  not  belong  to  the  oxygen  at  first  contained  in  the  jar.  They 
characterize  a  new  body,  the  result  of  the  combination  of  the 
sulphur  with  the  oxygen,  and  formed  by  chemical  action. 

Carbon,  sulphur,  and  oxygen  are  simple  bodies  or  elements. 
They  are  so  called  because  from  neither  of  them  can  more  than 
one  kind  of  matter  be  obtained.  But  when  the  charcoal  in 
burning  unites  with  the  oxygen,  the  carbonic  acid  which  re- 
sults from  the  union  contains  two  kinds  of  matter, — carbon  and 
oxygen  ;  and  these  two  elements  are  united  in  such  an  intimate 
manner  that  the  body  which  contains  both  does  not  resemble 
either  carbon  or  oxygen:  it  is  endowed  with  new  properties 
which  do  not  in  any  manner  recall  those  of  the  elements  which 
constitute  it.  In  fact,  it  is  a  new  substance,  a  compound  body 
formed  by  the  combination  of  the  matter  of  the  charcoal  with 
the  matter  of  the  oxygen. 

Considering  the  preceding  facts,  we  may  give  to  chemistry 
the  following  definition :  chemistry  studies  those  intimate  ac- 
tions of  bodies  upon  each  other  which  modify  their  natures 
and  cause  a  complete  and  lasting  change  in  their  properties. 

Iron  may  be  reduced  to  a  fine  powder.  This  may  be  mixed 
with  sulphur  itself  reduced  to  powder,  and  if  the  mixture  be 
sufficiently  intimate,  it  will  present  neither  the  lemon-yellow 
color  of  sulphur  nor  the  gray-black  of  finely-divided  iron. 
Nevertheless,  a  homogeneous  substance  cannot  be  formed  in 
this  manner.  If  the  powder  be  examined  under  the  micro- 
scope, the  particles  of  iron  may  be  recognized  disseminated 
among  those  of  the  sulphur,  but  not  confounded  with  them. 
By  the  aid  of  a  magnet  the  iron  may  be  separated.  On  the 
other  hand,  if  the  mass  be  thrown  into  water,  the  particles  of 
iron  will  sink  first  to  the  bottom,  while  the  lighter  particles  of 
sulphur  remain  in  suspension.  Thus,  after  having  triturated 
the  sulphur  and  iron  together,  not  only  can  each  substance  be 
recognized  in  the  mass,  but  they  can  be  again  separated  by 
mechanical  means.  Here  there  has  been  no  chemical  action, 
but  simply  a  mixture.  If,  however,  this  mixture  be  heated, 
the  sulphur  will  first  be  seen  to  melt,  and  afterwards  the 


INTRODUCTION.  11 

whole  mass  will  blacken  and  enter  into  fusion  if  the  tempera- 
ture be  sufficiently  elevated.  After  cooling,  it  is  perfectly  ho- 
mogeneous, and  neither  iron  nor  sulphur  can  be  recognized. 
Both  have  disappeared  as  such,  and  in  their  place  is  found  a 
substance  having  new  properties  ;  it  is  the  sulphide  of  iron. 

They  have  disappeared,  but  their  substance  is  not  lost ;  and 
it  may  be  proved  by  experiment  that  the  weight  of  the  sul- 
phide of  iron  produced  is  exactly  equal  to  the  sum  of  the 
weights  of  the  iron  and  the  sulphur.  The  ponderable  matter 
of  the  iron  is  then  added  to  the  ponderable  matter  of  the  sul- 
phur, and  has  formed  with  it  a  union  so  intimate  that  there 
results  a  new  body,  the  smallest  particles  of  which  are  per- 
fectly similar  to  each  other  and  to  the  entire  mass.  This  ex- 
ample and  a  thousand  others  that  might  be  given  prove  that 
when  bodies  combine  there  is  neither  loss  nor  creation  of  mat- 
ter. The  result  of  the  combination,  that  is,  the  compound 
body,  contains  the  whole  of  the  substance  and  nothing  more 
than  the  substance  of  the  combining  bodies.  This  is  an  essen- 
tial characteristic  of  chemical  combination. 

The  force  which  presides  over  chemical  combination  is  called 
affinity.  It  is  important  that  this  force  be  distinguished  from 
another  which  is  often  opposed  to  it,  and  which  is  cohesion. 

In  order  to  reduce  to  powder  a  solid  substance,  such  as 
pyrites  or  sulphide  of  iron,  it  is  necessary  to  overcome  the 
resistance  opposed  by  the  particles  of  the  mass  to  their  separa- 
tion. This  resistance  is  due  to  a  special  force,  which  brings 
and  maintains  in  relation  to  each  other  the  homogeneous  par- 
ticles of  the  sulphide  of  iron,  as  indeed  of  all  solid  bodies. 
This  is  cohesion.  The  particles  which  are  bound  together  by 
this  force  are  not  only  those  minute  particles  which  are  visible 
to  the  naked  eye  or  under  the  microscope,  and  of  which  the 
most  impalpable  powder  of  a  solid  body  is  composed.  Such 
particles  still  present  a  magnitude  that  can  be  measured ;  they 
must  be  considered  as  little  masses,  so  to  speak,  indivisible  by 
the  mechanical  means  at  our  command,  but  formed  in  reality 
of  particles  still  smaller.  These  smallest  particles  of  a  solid 
body  which  are  bound  by  cohesion  are  called  molecules.  They 
are  not  in  immediate  contact  with  each  other.  In  a  perfectly 
compact  and  homogeneous  mass,  such  as  sulphide  of  iron,  the 
molecules  do  not  touch  each  other.  Between  them  exist 
spaces  of  considerable  magnitude,  compared  to  the  real  volume 
of  the  molecule.  This  idea  must  not  be  confounded  with  po- 


12  ELEMENTS   OF   MODERN   CHEMISTRY. 

rosity,  which  is  caused  by  those  accidental  spaces  which  form 
visible  pores  in  solid  bodies.  These  intermolecular  spaces  are 
those  which  separate  the  molecules  of  a  homogeneous  and  com- 
pact solid  body,  and  physicists  have  further  been  led  to  believe 
that  even  in  solid  bodies  the  molecules  are  not  perfectly  immo- 
bile, but  that  they  execute  vibratory  movements  in  the  spaces 
which  separate  them,  at  the  same  time  maintaining  their  own 
relative  positions. 

If  a  solid  body  be  heated,  a  part  of  the  heat  is  employed  in 
raising  the  temperature,  another  part  serves  to  increase  the 
distances  which  separate  the  molecules :  the  body  expands  in 
becoming  heated.  But,  as  the  distances  between  the  molecules 
increase  by  the  action  of  the  heat  and  the  effect  of  the  expan- 
sion, the  molecular  attraction  necessarily  becomes  more  feeble. 
Cohesion  is  thus  somewhat  diminished,  and  if  the  heat  be 
further  increased,  it  may  be  so  much  diminished  that  the  mole- 
cules, which  have  thus  far  been  maintained  in  definite  rela- 
tions, can  move  and  glide  freely  over  each  other;  the  solid 
body  then  enters  into  fusion  :  it  becomes  a  liquid.  The  liquid 
state  is  produced  by  a  diminution  of  cohesion,  and  is  charac- 
terized by  a  greater  mobility  of  the  molecules. 

But  if  the  liquid  body  be  still  further  heated,  at  a  certain 
point  the  additional  heat  may  produce  such  a  separation  of  the 
molecules  that,  already  freed  from  all  mutual  attraction,  they 
become  completely  independent  of  each  other.  This  is  char- 
acteristic of  the  gaseous  state. 

It  may  be  stated,  then,  that  cohesion  is  considerable  in  solid 
bodies,  but  slightly  energetic  in  liquids,  and  null  in  gases,  and 
we  have  just  seen  that  heat,  by  causing  the  changes  of  state  of 
a  body,  can  overcome  and  even  practically  abolish  this  physical 
force. 

Chemical  force  or  affinity  is  at  the  same  time  more  intimate 
and  more  powerful.  It  modifies  the  molecules  themselves.  It 
brings  heterogeneous  substances  into  intimate  relations,  and 
thus  produces  new  molecules.  A  consideration  of  the  examples 
already  cited  may  indicate  more  clearly  the  meaning  of  this 
important  proposition. 

We  have  brought  together  sulphur  and  iron,  and  by  their 
reciprocal  action  and  the  aid  of  heat  there  has  been  formed  a 
new  body, — sulphide  of  iron.  We  know  that  the  smallest  mass 
of  sulphur  we  can  obtain  is  composed  of  a  collection  of  per- 
fectly homogeneous  molecules,  aggregated  by  cohesion.  In  each 


INTRODUCTION.  13 

of  them  but  one  kind  of  matter  can  be  found.  It  is  the  same 
with  iron :  the  particles  of  this  metal  are  perfectly  homoge- 
neous. Sulphur  and  iron  are  simple  bodies  or  elements. 

Let  us  now  consider  the  sulphide  of  iron  which  results  from 
their  combination.  This  body  also  is  formed  of  a  collection  of 
molecules,  bound  together  by  cohesion  and  perfectly  similar  to 
each  other,  but  not  homogeneous,  for  in  each  molecule  we  dis- 
tinguish two  kinds  of  matter, — sulphur  and  iron. 

It  cannot  be  admitted  that  these  two  substances  are  con- 
founded in  the  molecule,  or  that  the  effect  of  the  combination 
of  sulphur  with  iron  is  an  interpenetration  of  the  two  bodies 
so  intimate  that  they  both  disappear  in  what  might  be  called  a 
homogeneous  mixture.  On  the  contrary,  it  is  supposed  that 
the  combination  results  from  the  juxtaposition  of  two  infinitely 
small  masses,  each  of  which  possesses  a  real  magnitude  and  a 
constant  weight. 

These  little  masses  that  no  force,  chemical  or  physical,  can 
divide  further,  constitute  the  atoms.  In  each  molecule  of  sul- 
phide of  iron  there  exist  two  of  these  masses, — one  of  sulphur 
and  one  of  iron ;  and  the  atom  of  sulphur  and  the  atom  of 
iron  are  bound  together,  but  not  confounded,  by  chemical  force. 
And  when  sulphur  combines  with  iron  it  is  because  the  atoms 
of  the  sulphur  arrange  themselves  in  juxtaposition  with  those 
of  the  iron,  and  it  is  affinity  which  brings  about  the  action. 

When  these  atoms  again  separate,  the  sulphide  of  iron  is  said 
to  decompose.  When  it  attracts  the  atoms  of  another  body,  it 
is  said  to  combine  with  that  body. 

If  sulphide  of  iron  remain  for  some  time  exposed  to  moist 
air,  its  surface  becomes  covered  with  an  efflorescence  formed  of 
a  saline  matter.  In  this  case  it  has  attracted  one  of  the  ele- 
ments of  the  air,  oxygen,  with  which  it  has  combined  to  form 
green  vitriol  or  sulphate  of  iron. 

The  molecules  of  oxygen,  upon  which  cohesion  has  no  hold, 
the  body  being  gaseous,  are  each  formed  of  two  atoms,  but 
these  atoms  are  of  the  same  kind ;  the  molecules  of  sulphide 
of  iron,  on  the  contrary,  are  each  formed  of  two  unlike  atoms, — 
one  of  sulphur  and  one  of  iron.  These  latter  attract  four  atoms 
of  oxygen,  which  constitute  two  molecules  of  that  gas,  and 
these  group  themselves  around  the  atom  of  sulphur  and  the 
atom  of  iron,  forming  with  them  one  single  molecule,  more 
complex  than  the  primitive  molecule  of  sulphide  of  iron,  for 
it  contains  in  addition  four  atoms  of  oxygen. 

2 


14  ELEMENTS    OF    MODERN    CHEMISTRY. 


1  molecule  1  molecule      1  molecule 

sulphide  of  iron.  oxygen.          oxygen. 


®    ©  0 


fixes 


and  there  results 

1  molecule 
ilpliate  of  iron. 


^ 


It  is  seen  from  what  precedes  that  the  words  molecule  and 
atom  are  far  from  being  synonyms.  The  chemical  molecule 
constitutes  a  whole  of  which  the  atoms  form  the  parts,  and 
these  atoms  are  held  together  by  affinity.  In  the  preceding 
figure,  this  exchange  of  affinities  between  the  atoms  is  indi- 
cated by  lines  of  union. 

Chemical  molecules  have  been  well  compared  to  edifices: 
the  atoms  constitute  the  materials,  and  it  is  readily  conceived 
that  such  molecular  edifices  differ  from  each  other  according 
to  the  nature,  number,  and  arrangement  of  the  atoms,  that  is, 
the  materials  composing  them. 

An  edifice  may  be  enlarged  by  the  addition  of  new  parts  :  it 
may  be  reduced  in  size  or  it  may  be  entirely  demolished.  In 
the  same  manner  a  chemical  molecule  may  be  increased  by  the 
annexation  of  new  atoms,  or  diminished  by  the  separation  of 
some  of  those  which  it  already  contains.  In  the  first  case 
there  is  combination,  in  the  second,  decomposition. 

We  may  still  further  consider  these  phenomena  of  combina- 
tion and  decomposition. 

Since  the  combination  of  two  bodies  results  from  the  recip- 
rocal action  of  their  atoms,  and  has  for  effect  a  change  in  the 
nature  of  the  molecules,  it  is  evident  that  it  can  only  take 
place  when  these  atoms,  and  consequently  the  molecules,  are 
brought  into  intimate  relations  ;  or  more  precisely,  when  the 
molecules  of  one  of  the  bodies  enter  within  the  sphere  of 
action  of  the  molecules  of  the  other  body.  And  this  sphere 
of  action  is  very  limited,  for  the  affinity  or  elective  attraction 
of  the  atoms  is  only  exercised  at  infinitely  small  distances. 


INTRODUCTION.  15 

It  results  that  affinity  is  often  retarded  by  cohesion,  which 
maintains  the  relations  between  the  molecules  of  a  solid  body. 
These  two  forces  are  frequently  in  opposition,  and  that  the 
first  may  attain  the  supremacy  it  is  necessary  that  the  other 
shall  yield.  To  make  manifest  or  to  increase  the  affinity  be- 
tween two  bodies,  it  is  then  necessary  to  diminish  their  cohe- 
sion. On  this  condition  the  molecules  can  enter  within  the 
spheres  of  their  reciprocal  attraction,  and  the  atoms  of  one 
body  can  attract  those  of  the  other. 

It  has  been  seen  from  one  of  the  experiments  already  cited 
that  in  order  to  combine  iron  with  sulphur  it  is  necessary  to 
elevate  the  temperature.  Now,  the  heat,  by  fusing  the  sul- 
phur, diminishes  its  cohesion,  and,  giving  its  molecules  freedom 
of  motion,  puts  them  into  more  intimate  contact  with  those  of 
the  iron.  Chemical  action  then  commences. 

Instead  of  heating  the  sulphur  and  iron  to  bring  about 
chemical  action,  it  would  be  sufficient  to  moisten  the  mixture 
with  water.  By  the  intervention  of  this  liquid  the  particles 
of  sulphur  and  of  iron  are,  as  it  were,  cemented  together  and 
thus  brought  into  more  intimate  relations.  For  a  stronger 
reason  can  chemical  action  between  two  solids  be  facilitated  by 
dissolving  them  both  in  water  and  mixing  the  solutions.  Dis- 
solved, they  themselves  assume  the  liquid  state  and  lose,  in 
great  part,  their  cohesion.  The  ancients  understood  the  in- 
fluence of  the  liquid  state  upon  reactions,  and  stated  it  with 
exaggeration  :  Corpora  non.agunt  nisi  soluta. 

Although  the  liquid  state  facilitates  chemical  reactions,  it 
does  not  follow  that  it  always  determines  them.  Frequently 
liquids  and  even  gases,  after  being  mixed,  must  be  heated 
before  they  will  react  upon  each  other. 

Experiment. — In  a  glass  tube  (Fig.  3)  two  gases,  oxygen 
and  hydrogen,  are  mixed  in  the  proportion  of  one  volume  of 
the  first  to  two  of  the  second.  Although  the  mixture  is  per- 
fectly homogeneous  and  very  intimate,  and  although  the  cohe- 
sion of  the  gaseous  molecules  is  null,  no  action  takes  place. 
But  as  soon  as  the  mixture  is  heated  by  approaching  a  lighted 
taper  to  the  mouth  of  the  tube,  combination  takes  place  ener- 
getically. An  explosion  occurs  and  the  two  gases  unite,  form- 
ing water.  In  this  case  the  heat  has  determined  combination 
by  increasing  the  intensity  of  the  movements  which  animate 
the  molecules  of  each  gas,  and  so  bringing  the  molecules  of  the 
one  within  the  sphere  of  attraction  of  those  of  the  other. 


16  ELEMENTS   OF    MODERN   CHEMISTRY. 

The  electric  spark  produces  the  same  effect,  and  it  probably 
acts  by  the  heat  which  it  communicates  to  the  mixture. 


FIG.  3. 

More  rarely  combination  is  brought  about  by  the  influence 
of  light. 

If  a  small  bottle  be  filled  with  a  mixture  of  equal  volumes 
of  hydrogen  and  chlorine  gases,  and  then  thrown  into  the  air 
so  that  it  may  be  struck  by  the  direct  rays  of  the  sun,  the 
combination  of  the  two  gases  takes  place  instantly  and  with 
explosion. 

Such  are  some  of  the  conditions  which  favor  or  determine 
chemical  combination.  Let  us  now  study  the  circumstances 
which  accompany  these  phenomena. 

Experiment. — If  sulphur  be  strongly  heated  in  a  small  glass 
flask  until  it  begins  to  boil,  and  some  copper  turnings  be  then 
thrown  into  the  flask,  a  brilliant  incandescence  takes  place  im- 
mediately. It  is  produced  by  the  combination  of  the  two 
bodies.  Charcoal,  sulphur,  and  phosphorus  produce  a  brilliant 
light  when  they  are  burned  in  oxygen.  Their  combination 
with  the  gas  takes  place  with  evolution  of  luminous  heat. 

Whenever  a  combustible  body  of  whatever  nature  burns  in 
the  air,  the  heat  and  light  are  developed  by  the  combination 
of  the  body  with  oxygen,  one  of  the  elements  of  the  air.  In 
general,  all  chemical  combinations  give  rise  to  the  production  of 
heat,  more  or  less  intense ;  in  certain  cases  it  is  luminous,  but 
more  often  it  is  obscure ;  sometimes  it  is  scarcely  perceptible. 

While  heat  acts  as  the  determining  cause  of  a  great  number 


INTRODUCTION.  17 

of  combinations,  and  while  it  is  the  result  of  such  combination, 
it  may  play  still  another  role  in  chemical  reactions.  In  place 
of  favoring  combination,  it  may  act  in  the  opposite  manner, 
separating  atoms  which  are  united  by  chemical  attraction. 

Mercury  retains  indefinitely  its  brilliant  surface  when  ex- 
posed to  the  air  at  ordinary  temperatures,  but  at  a  temperature 
near  its  boiling-point  it  slowly  attracts  the  oxygen  of  the  air, 
and  becomes  covered  with  an  orange-red  powder,  which  is  oxide 
of  mercury.  In  this  case  heat  has  assisted  the  formation  of  a 
compound. 

If,  however,  this  red  powder  be  heated  in  a  small  retort  to  a 
temperature  near  redness,  it  is  again  resolved  into  mercury, 
which  appears  in  drops  in  the  neck  of  the  retort,  and  into 
oxygen  which  may  be  collected. 

In  this  case  an  intense  heat  breaks  up  the  compound  which 
is  formed  at  a  temperature  less  elevated ;  it  occasions  a  decom- 
position. 

Heat  acts  thus  in  a  great  number  of  cases.  A  body  is  said 
to  decompose  when  the  elements  composing  it  are  separated 
from  each  other. 

The  electric  spark  may  occasion  such  separation  when  it  is 
passed  through  compound  gases.  If  a  series  of  electric  dis- 
charges be  passed  through  ammonia  gas,  the  latter  is  decom- 
posed, that  is,  resolved  into  its  two  elements, — nitrogen  and 
hydrogen. 

In  like  manner,  the  current  of  the  voltaic  pile  decomposes 
a  great  number  of  chemical  compounds,  the  elements  of  which 
separate  and  appear,  each  at  its  appropriate  pole  of  the  bat- 
tery. The  decomposing  action  exerted  by  the  galvanic  current 
upon  chemical  compounds  was  discovered  about  the  commence- 
ment of  the  present  century  by  Nicholson  and  Carlisle.  These 
physicists  were  the  first  to  decompose  water  by  the  voltaic 
current. 

Lastly,  light  may  decompose  certain  bodies,  among  which 
are  a  great  number  of  the  compounds  of  silver.  The  art  of 
photography  is  founded  upon  the  decomposing  action  of  light 
upon  certain  of  these  combinations. 

There  is  a  certain  class  of  decompositions  which  it  is  impor- 
tant to  consider  with  attention.  They  are  occasioned  by  the 
intervention  of  more  powerful  affinities  than  those  which  main- 
tain united  the  elements  of  a  compound  body. 

If  copper  be  heated  in  the  air,  it  attracts  oxygen  and  is  con- 

2* 


18 


ELEMENTS    OF    MODERN    CHEMISTRY. 


verted  into  a  black  powder,  a  compound  of  oxygen  and  copper, 
which  is  called  oxide  of  copper.  The  affinity  which  unites  the 
two  bodies  is  considerable  ;  it  cannot  be  overcome  by  the  ac- 
tion of  heat  alone ;  at  any  ordinary  temperature  to  which  the 
oxide  so  formed  may  be  exposed,  the  atoms  of  copper  still  re- 
main intimately  associated  with  those  of  the  oxygen.  But  if 
this  oxide  be  mixed  with  powdered  charcoal  and  then  heated, 
a  moment  arrives  when  the  affinity  of  the  charcoal  for  the  oxy- 
gen is  superior  to  that  of  the  copper.  The  atoms  of  oxygen 
then  abandon  the  copper  and  combine  with  the  charcoal,  thus 
forming  a  new  compound,  carbonic  acid,  which  is  disengaged 
in  the  form  of  gas.  Here  there  is  at  the  same  time  decompo- 
sition and  combination.  The  molecules  of  oxide  of  copper  are 
decomposed ;  those  of  carbonic  acid  are  formed. 

Nothing  is  created  in  combinations ;  nothing  is  lost  in  de- 
compositions. In  the  preceding  experiment  only  copper  re- 
mains ;  the  charcoal  and  oxygen  have  disappeared,  but  their 
substance  is  not  lost.  All  of  the  matter  of  the  charcoal  is 


FIG.  4. 


found  combined  with  all  of  the  matter  of  the  oxygen  in  the 
product  of  their  combination,  the  carbonic  acid,  in  such  a 
manner  that  the  weight  of  the  latter  added  to  the  weight  of 
the  copper  remaining,  exactly  represents  the  weight  of  the 
oxide  of  copper  and  charcoal. 


INTRODUCTION.  19 

Experiment. — Some  oxide  of  mercury,  of  which  we  have 
seen  the  decomposition  by  heat,  may  be  placed  in  a  tube 
through  which  is  passed  a  current  of  hydrochloric  acid  gas,  a 
gas  composed  of  chlorine  and  hydrogen  (Fig.  4).  An  ener- 
getic reaction  takes  place.  The  orange-red  powder  is  converted 
into  a  white  crystalline  substance,  and  much  heat  is  produced. 
At  the  same  time  a  small  quantity  of  liquid  condenses  in  the 
bulb.  This  is  water,  and  the  white  powder  formed  is  mercuric 
chloride,  or  corrosive  sublimate,  a  compound  of  mercury  and 
chlorine.  The  hydrochloric  acid  has  converted  the  mercuric 
oxide  into  mercuric  chloride.  The  mercury,  at  first  combined 
with  oxygen,  is  now  combined  with  chlorine.  But  what  has 
become  of  the  oxygen  ?  It  has  combined  with  the  hydrogen 
of  the  hydrochloric  acid,  forming  water.  We  have  brought 
into  presence  of  each  other  two  compound  bodies : 

Mercuric  oxide, 
Hydrochloric  acid, 

and  from  their  reciprocal  action  two  new  compounds  result : 

Mercuric  chloride, 

Water  or  oxide  of  hydrogen. 

This  reaction  has  then  occasioned  an  interchange  of  elements. 
The  mercury  of  the  mercuric  oxide  has  combined  with  the 
chlorine  of  the  hydrochloric  acid,  and  the  oxygen  has  left  the 
mercury  and  combined  with  the  hydrogen,  which  was  aban- 
doned by  the  chlorine.  The  reaction  has  been  as  easy  as 
energetic,  thanks  to  the  intervention  of  two  affinities,  for  the 
affinity  of  chlorine  for  mercury  has  been  aided  by  that  of  hy- 
drogen for  oxygen.  Two  molecules  are  decomposed,  and  two 
new  molecules  are  formed  by  an  exchange  which  may  be  rep- 
resented in  the  following  manner : 

BEFORE    THE    REACTION. 

Mercury     +  Oxygen   =  Mercuric  oxide. 
Hydrogen  +  Chlorine  =  Hydrochloric  acid. 

DURING   THE    REACTION. 


AFTER   THE    REACTION. 

Mercury     +  Chlorine  =  Mercuric  chloride. 
Hydrogen  +  Oxygen    =  Water. 


20  ELEMENTS    OP    MODERN    CHEMISTRY. 

Such  reactions,  characterized  by  an  interchange  of  elements, 
are  called  double  decompositions.  They  are  the  more  usual 
reactions  in  chemistry. 

The  examples  cited  have  been  demonstrated  by  experiments 
easy  to  comprehend  and  to  repeat,  and  are  sufficient  to  give  an 
idea  of  chemical  phenomena.  We  have  seen  how,  on  the  con- 
tact of  two  heterogeneous  bodies,  this  elective  attraction,  which 
is  called  affinity  and  which  sets  in  motion  the  smallest  particles 
of  bodies,  comes  into  play  to  produce  either  combination  or 
decomposition ;  we  have  seen  how  this  force  modifies  the 
chemical  molecules  either  by  interposing  other  molecules,  or 
under  the  influence  of  physical  forces,  such  as  heat  and  elec- 
tricity. The  study  of  all  these  phenomena  constitutes  chem- 
istry, the  science  of  molecular  changes  ;  a  science  grand  in 
purpose  and  in  magnitude,  since  it  penetrates  to  the  very 
nature  of  the  bodies  surrounding  us ;  a  science  unlimited  in 
its  applications,  since  through  it  we  learn  to  know  and  control 
the  powerful  forces  which  are  at  work  in  the  most  intimate 
structure  of  matter. 

If  we  trace  the  acquired  facts  to  the  most  obvious  and  most 
certain  conclusion,  we  must  admit  the  diversity  of  matter. 
There  exists,  indeed,  a  certain  number  of  bodies,  each  of  which, 
when  submitted  to  the  various  tests  resulting  from  the  applica- 
tion of  physical  and  chemical  forces,  furnishes  but  one  and  the 
same  substance,  and  it  is  impossible  to  obtain  anything  else 
than  this  substance  from  the  body.  We  maintain,  then,  until 
proved  to  the  contrary,  that  each  of  these  bodies  contains  but 
a  single  kind  of  matter,  and  they  are  called  simple  bodies  or 
elements.  The  chemical  forces  reside,  as  has  been  seen,  in  the 
most  remote  particles,  in  the  atoms  of  these  bodies.  In  uniting 
together,  the  elements  form  compound  bodies,  and  it  has  al- 
ready been  stated  that  such  combinations  result  from  the  juxta- 
position of  the  atoms  which  attract  each  other.  The  idea  of 
atoms  is  an  hypothesis,  but  the  hypothesis  is  based  upon  nu- 
merous and  important  facts,  which  it  weaves  together  in  the 
most  natural  manner.  It  is  more  than  an  hypothesis :  it  is  a 
theory.  Chemists  have  universally  adopted  it,  for  it  has  ren- 
dered immense  service  to  the  science.  Let  us  proceed,  then, 
to  a  consideration  of  the  facts  upon  which  it  is  based. 


DEFINITE   PROPORTIONS,  EQUIVALENTS. 


21 


FIG.  5. 


DEFINITE   PROPORTIONS,  EQUIVALENTS. 

The  proportions  by  weight  according  to  which  bodies  combine  are  invaria- 
ble for  each  combination — Those  proportions  are  the  equivalents — Ex- 
periments demonstrating  this  fact. 

Experiment. — A  test-glass  (Fig.  5)  contains  a  liquid  which 
is  universally  known  as  sulphuric  acid.  Although  largely  di- 
luted with  water,  that  is, 
mixed  with  a  large  quan- 
tity of  that  liquid,  it  still 
manifests  its  presence  by 
energetic  properties.  It 
has  a  very  sour  and  cor- 
rosive taste, — a  quality  of 
an  acid.  If  a  few  drops 
of  blue  litmus  solution  be 
added  to  it  the  blue  color 
instantly  changes  to  bright 
red.  Another  glass  contains 
a  solution  of  caustic  potash 
or  potassium  hydrate.  This 
substance  possesses  a  strong,  lye-like,  alkaline  taste,  very  easy 
to  distinguish  from  that  of  the  acid.  The  color  of  the  blue 
litmus  is  not  affected  by  this  liquid,  but  if  a  few  drops  of  the 
litmus  solution,  previously  reddened  by  an  acid,  be  added,  the 
blue  color  is  immediately  restored.  This  caustic  substance 
has  properties  which  are  different  from  those  of  acids,  and 
which  are  called  basic  or  alkaline  properties.  Potassium 
hydrate  is  an  alkali  or  powerful  base. 

If  now  the  alkaline  liquid,  which  has  a  blue  color,  be  poured 
drop  by  drop  into  the  acid,  which  is  red,  and  the  mixture  be 
stirred  with  a  glass  rod,  a  moment  arrives  when  the  red  color 
of  the  acid  liquid  changes  to  blue.  Exactly  at  this  moment 
we  have  a  solution  which  has  no  action  upon  litmus ;  it  will 
not  redden  the  blue  solution,  neither  will  it  restore  the  blue 
color  to  the  red.  This  may  be  demonstrated  by  dipping  into 
it  first  a  red  and  then  a  blue  litmus-paper.  Furthermore,  this 
liquid  possesses  neither  the  acid  taste  of  the  oil  of  vitriol  nor 
the  alkaline  taste  of  the  caustic  potash,  but  its  taste  is  salty. 

By  their  mixture  and  reciprocal  action  the  sulphuric  acid 
and  the  potash  have  lost  the  energetic  properties  which  they 


22  ELEMENTS    OF    MODERN    CHEMISTRY. 

manifested  in  the  free  state.  They  are  exactly  saturated ;  they 
are  neutralized.  That  is,  the  liquid  which  now  contains  both, 
or  more  properly  the  product  of  their  reaction,  is  neither  acid 
nor  alkaline  ;  it  is  neutral,  and  its  neutrality  is  manifested  both 
by  its  indifference  to  vegetable  colors  and  by  its  effects  on  our 
organs  of  sense.  There  is  no  excess,  neither  of  sulphuric  acid 
nor  of  potash,  but  the  two  bodies  have  reacted  exactly  upon 
each  other  and  have  both  disappeared,  and  from  their  recipro- 
cal action  two  new  bodies  result, — a  salt  called  potassium  sul- 
phate, and  water. 

Whenever  sulphuric  acid  is  thus  saturated  by  potash,  there 
arrives  a  moment  when  the  whole  of  the  acid  is  precisely  neu- 
tralized by  the  alkali,  and  when  the  two  bodies  are  converted, 
without  residue  of  either  one  or  the  other,  into  potassium  sul- 
phate and  water ;  and  it  is  always  easy  to  recognize  the  instant 
at  which  this  effect  is  produced  by  the  action  of  the  liquid  upon 
vegetable  colors,  such  as  solution  of  litmus,  or  syrup  of  violets. 
The  latter  is  reddened  by  an  acid,  changed  to  green  by  an 
alkali,  and  assumes  its  natural  violet  tint  when  the  neutral 
point  is  reached.  Now,  it  has  been  found  that  this  last  effect 
is  only  produced  when  the  acid  and  the  alkali  are  mixed  in 
certain  proportions,  which  remain  invariable,  whatever  may  be 
the  quantities  which  are  mixed.  In  other  words,  it  has  been 
found  that  the  quantities  of  sulphuric  acid  and  potash  which 
reciprocally  neutralize  each  other  and  form  potassium  sulphate, 
maintain  a  constant  ratio  to  each  other.  It  may  be  easily  proved 
that  when  the  state  of  neutrality  has  been  once  attained,  it  is 
immediately  passed  and  disturbed  by  the  least  excess  of  either 
acid  or  base  that  may  be  added  to  the  liquid.  This  is  made 
evident  by  the  immediate  change  in  the  color  of  the  liquid  to 
either  red  or  green. 

Thus,  in  order  to  form  sulphate  of  potassium  with  a  given 
quantity  of  sulphuric  acid,  it  is  necessary  to  add  an  invariable 
quantity  of  potash ;  and  if  the  quantity  of  sulphuric  acid  be 
increased  by  a  third,  or  in  any  proportion  whatever,  it  is  neces- 
sary to  increase  by  a  third,  or  in  the  same  proportion,  the  quan- 
tity of  potash. 

Experiments  of  this  kind  have  been  made  with  other  acids 
and  other  bases,  and  have  introduced  into  the  science  the  fun- 
damental notion  that  these  bodies  react  upon  each  other  in 
definite  proportions  to  form  salts,  and  that  consequently  the 
composition  of  the  latter  bodies  is  perfectly  fixed.  A  given 


DEFINITE    PROPORTIONS,  EQUIVALENTS.  23 

quantity  of  any  acid  whatever,  invariably  saturates  a  fixed 
quantity  of  the  same  base.  This,  then,  is  the  first  point. 

It  may  be  added  that  similar  researches  made  towards  the 
close  of  the  last  century  have  led  to  a  not  less  important  result, 
namely,  the  respective"  quantities  of  several  acids  which  satu- 
rate a'given  weight  of  one  base  are  exactly  proportional  to  the 
quantities  of  the  same  acids  which  saturate  a  given  weight  of 
another  base.  The  law  which  governs  the  composition  of  salts 
was  discovered  towards  the  close  of  the  last  century  by  a  Ger- 
man chemist,  Richter.  We  cannot  now  expose  it  in  detail ; 
such  development  will  be  better  placed  and  better  understood 
in  that  part  of  this  work  which  treats  of  the  formation  of  salts. 
For  the  present  it  is  sufficient  to  state  that  die  law  mentioned 
is  a  consequence  of  the  law  of  definite  proportions,  and  that 
the  latter  law  is  universal.  It  applies  not  only  to  the  reaction 
of  acids  upon  bases,  but  is  true  for  all  chemical  combinations. 
It  may  be  thus  expressed : 

The  relative  weights  according  to  which  bodies  combine  are 
invariable  for  each  combination. 

There  is  one  feature  of  the  laws  which  control  the  composi- 
tion by  weight  of  bodies  that  it  is  important  to  comprehend  well. 

It  may  be  best  illustrated  by  experiment : 

100  gr.  of  mercury  are  put  into  the  presence  of  chlorine 
gas,  a  body  possessing  very  powerful  affinities.  In  this  man- 
ner mercuric  chloride  or  corrosive  sublimate  is  formed,  and  it 
is  found  that  35.5  gr.  of  chlorine  are  necessary  to  convert  100 
gr.  of  mercury  into  this  compound.  These  figures — 100  and 
."..'."» — express  the  invariable  ratio  in  which  these  elements  are 
combined  in  corrosive  sublimate.  Here  we  have  the  definite 
proportions. 

Now  let  the  135.5  gr.  of  corrosive  sublimate  be  dissolved  in 
water,  and  a  plate  of  copper  be  placed  in  the  solution ;  this 
metal  will  displace  the  mercury,  and  combining  with  the  35.5 
gr.  of  chlorine  will  form  with  it  cupric  chloride,  which  will 
remain  in  solution,  coloring  the  liquid  green.  The  100  gr.  of 
mercury  are  then  precipitated,  and  it  will  be  found  that  31.75 
gr.  of  copper  have  entered  the  solution  and  actually  combined 
with  35.5  gr.  of  chlorine. 

Into  this  solution  of  cupric  chloride  a  plate  of  zinc  is  now 
plunged ;  all  of  the  copper  is  precipitated  in  its  turn,  and  33 
gr.  of  zinc  enter  into  combination  with  die  35.5  gr.  of  chlorine, 
forming  zinc  chloride. 


24  ELEMENTS   OF   MODERN   CHEMISTRY. 

The  35.5  gr.  of  chlorine  have  now  been  combined  success- 
ively with 

100  gr.  of  mercury, 
31.75  gr.  of  copper, 
33  gr.  of  zinc. 

These  numbers,  which  express  the  respective  quantities  of 
mercury,  copper,  and  zinc  which  combine  with  the  same  quan- 
tity of  chlorine,  may  be  called  the  equivalents  of  these  metals. 
In  fact,  these  quantities  are  equivalent  to  each  other  in  relation 
to  the  same  quantity  of  chlorine,  the  experiment  having  shown 
us  that  in  order  to  displace  100  gr.  of  mercury  combined  with 
35.5  gr.  of  chlorine  it  is  necessary  to  employ  31.75  gr.  of 
copper  or  33  gr.  of  zinc. 

To  continue,  100  gr.  of  mercury  are  combined  with  oxygen, 
and  it  is  found  that  this  quantity  of  the  metal  requires  8  gr.  of 
oxygen  to  form  the  red  powder  called  mercuric  oxide. 

But  how  much  oxygen  is  necessary  to  form  cupric  oxide 
with  31.75  gr.  of  copper?  Remarkable  as  it  seems,  exactly 
8  gr.  are  required,  and  8  gr.  are  also  requisite  to  form  oxide 
of  zinc  with  33  gr.  of  zinc. 

100  gr.  of  mercury, 
31.75  gr.  of  copper, 
33  gr.  of  zinc, 

which  are  equivalent  compared  to  35.5  gr.  of  chlorine,  are  then 
also  equivalent  in  relation  to  8  gr.  of  oxygen. 

Chlorine  itself  may  be  oxidized,  and  there  exists  a  gaseous 
compound  of  chlorine  and  oxygen  which  contains  precisely  8 
gr.  of  oxygen  for  35.5  gr.  of  chlorine. 

Thus,  there  are  required 


35.5  gr  of  chlorine  to  form  chlorides  with. 
8  gr.  of 

and  also 


8  gr.  of  oxygen  to  oxidize    .......  zinc, 


.    (  iJ^ 
(  33  gr.  of  zi 


8  gr.  of  oxygen  to  oxidize  35.5  gr.  of  chlorine. 

In  general,  if 

A,  B,  C,          combine  with  D, 

A,  B,  C,  combine  also  with  E, 

and  further,  D  combines  with  E, 

the  letters  A,  B,  C,  D,  E,  representing  the  weights  of  the  dif- 
ferent elements  which  enter  into  combination,  or  the  propor- 
tions according  to  which  the  bodies  combine  among  themselves. 


MULTIPLE   PROPORTIONS.  25 

They  are  expressed  by  numbers  that  have  been  called  combin- 
ing weights  or  equivalents  ;  these  represent  the  ratio  of  weights 
or  the  relative  weights.  They  are  indeed  relative  to  a  unit 
which  has  served  as  a  term  of  comparison,  and  which  is  the 
equivalent  of  hydrogen.  That  is,  the  quantity  of  hydrogen 
which  combines  with  35.5  of  chlorine  being  1,  the  equivalent 
quantities  of  oxygen,  zinc,  copper,  and  mercury  will  be  repre- 
sented by  the  numbers  8 — 33 — 31.75—100. 

These  are  the  facts  of  experiment.  Let  33  gr.  of  zinc  be 
treated  with  hydrochloric  acid,  the  latter  is  immediately  de- 
composed ;  its  chlorine  combines  with  the  zinc,  forming  chlo- 
ride of  zinc,  and  its  hydrogen  is  disengaged.  In  this  experi- 
ment the  hydrogen  of  the  hydrochloric  acid  is  simply  displaced 
by  the  zinc.  Now,  33  gr.  of  this  metal  will  displace  exactly 
1  gr.  of  hydrogen. 

It  is  seen  that  the  numbers  which  have  been  given  do  not 
express  absolute  quantities,  but  merely  the  relative  weights  ac- 
cording to  which  the  bodies  combine  or  replace  each  other  in 
compounds,  these  relative  weights  being  compared  to  that  of 
hydrogen,  which  is  taken  as  unity. 

Such  is  the  signification  of  the  numbers. 

inn         QI  *«.       OQ          oz  t  (which    represent 

100         31.75       33          3o.5  j    the  equivalents. 

of  of         of  of  of  of 

mercury,  copper,   zinc,    chlorine,    oxygen,   hydrogen. 

This  being  admitted,  in  order  to  determine  the  equivalent 
of  an  element  it  is  sufficient  to  find  the  quantity  of  that  ele- 
ment which  combines  either  with  1  of  hydrogen  or  with  a 
quantity  of  another  element  which  is  equivalent  to  1  of  hydro- 
gen, for  instance,  8  of  oxygen. 

The  notion  of  equivalents  can  be  understood  from  the  pre- 
ceding considerations ;  it  appears  as  a  consequence  of  the  law 
of  definite  proportions  ;  it  comprehends  certain  facts  relative 
to  the  laws  of  the  composition  of  bodies,  but  it  by  no  means 
represents  the  full  scope  of  these  laws.  The  following  devel- 
opments add  important  features. 

MULTIPLE    PROPORTIONS. 

Two  bodies  may  combine  in   several  proportions.     Thus, 

with  oxygen,  carbon  forms  two  compounds,  both  of  which  are 

gaseous.     The  less  rich  in  oxygen  is  carbon  monoxide ;  the 

richer  is  carbon  dioxide,  or  carbonic  acid  gas.     Dalton  was  th€f 

B  3 


26  ELEMENTS    OF    MODERN    CHEMISTRY. 

first  to  perceive  that  for  the  same  quantity  of  carton,  carbonic 
acid  contains  exactly  twice  as  much  oxygen  as  carbon  monoxide. 
He  made  analogous  observations  concerning  the  composition 
of  two  compounds  of  carbon  and  hydrogen,  the  monocarbide 
of  hydrogen  or  marsh  gas,  and  the  dicarbide  of  hydrogen  or 
olefiant  gas.  "From  these  observations  he  deduced  the  law  of 
multiple  proportions,  which  may  be  thus  stated :  when  two 
bodies,  simple  or  compound,  unite  in  several  proportions  to 
form  several  compounds,  the  weight  of  one  of  these  bodies 
being  considered  as  constant,  the  weights  of  the  other  vary 
according  to  a  simple  ratio. 

Thus,  taking  up  one  of  the  examples  given  above,  carbon 
unites  with  oxygen  in  two  proportions : 

Carbon  monoxide  contains  16  parts  of  oxygen  to  12  parts 
of  carbon. 

Carbon  dioxide  contains  32  parts  of  oxygen  to  12  parts  of 
carbon.  The  numbers  16  and  32  are  in  the  ratio  of  1  :  2. 

Nitrogen  forms  five  compounds  with  oxygen ;  if  such  quan- 
tities of  these  compounds  be  taken  as  contain  the  same  weight 
of  nitrogen,  the  weights  of  the  oxygen  will  be  proportional 
to  the  numbers  1,  2,  3,  4,  5. 

Nitrogen  monoxide  contains  for  28  parts  of  nitrogen  16  parts  of  oxygen. 
Nitrogen  dioxide  "  28  "  "  32  " 

Nitrogen  trioxide  "  28         «  "          48         "  " 

Nitrogen  tctroxide  "  28         "  "          64         "  " 

Nitrogen  pentoxide  "  28         "  "          80         " 

These  numbers,  16,  32,  48,  64,  80,  are  multiples  of  the  first 
by  the  numbers  1,  2,  3,  4,  5. 

Five  compounds  of  manganese  and  oxygen  are  known,  and 
similar  relations  exist  between  the  quantities  of  oxygen  con- 
tained in  these  compounds. 

The  first      contains  55  parts  of  manganese  to  16  of  oxygen. 
The  second        "         55  "  "  24 

The  third  "         55  "  "  32          " 

The  fourth         «         55  "  "  48          " 

The  fifth  "         55  «  "  56 

The  numbers  16,  24,  32,  48,  56  are  in  the  simple  propor- 
tion 1  :  1.5  :  2  :  3  :  3.5. 

Such  is  the  law  of  multiple  proportions  discovered  by 
Dalton. 

HYPOTHESIS    OF    ATOMS. 

The  brilliant  researches  of  Dalton  did  not  terminate  with 
the  acquisition  ot  facts,  but  sought  to  account  for  them  by  a 


GAY-LUSSAC'S   LAWS. — ATOMIC   THEORY.  27 

theoretical  conception.  Taking  up  the  old  idea  of  Lysippus 
and  the  word  of  Epicurus,  he  supposed  all  ponderable  matter 
to  be  composed  of  indivisible  particles  which  he  called  atoms. 
He  gave  a  precise  meaning  to  the  vague  and  ancient  notion  by 
considering  on  one  hand  that  the  atoms  of  each  kind  of  matter, 
of  each  element,  possess  an  invariable  weight,  and  on  the  other 
that  combination  between  different  kinds  of  matter  results  from 
the  juxtaposition  of  their  atoms.  Such  is  the  atomic  hypothe- 
sis, the  substance  of  which  we  have  already  indicated  in  treat- 
ing of  chemical  phenomena  in  a  general  manner.  It  permits 
a  simple  and  rational  interpretation  of  the  laws  of  the  compo- 
sition of  bodies,  and  establishes  between  these  laws  a  firm  bond 
of  theory. 

Indeed,  if  the  combination  of  bodies  results  from  the  juxta- 
position of  their  atoms,  the  latter  being  considered  as  indivisi- 
ble and  possessing  a  constant  weight  for  each  element,  it  is 
evident  that  combination  can  only  take  place  in  definite  pro- 
portions, for  these  proportions  represent  the  invariable  relations 
between  the  weights  of  the  atoms  which  are  in  juxtaposition. 
If,  on  the  other  hand,  one  body  may  combine  with  another  in 
several  proportions,  such  combination  can  only  take  place  by 
the  juxtaposition  of  1,  2,  3,  4,  etc.,  atoms  of  one  body  with 
one  or  more  atoms  of  the  other.  It  evidently  results  that  the 
weight  of  the  latter  body  being  constant,  the  weights  of  the 
other  in  these  various  combinations  must  be  multiples  of  each 
other. 

An  hypothesis  which  gives  such  a  simple  and  precise  ex- 
planation of  the  facts  relative  to  definite  and  multiple  propor- 
tions is  surely  worthy  of  attention.  It  acquires  still  further 
import  and  becomes  elevated  to  the  rank  of  a  theory  when  to 
these  facts  are  added  others  entirely  different  from  the  first, 
but  not  less  important. 

GAY-LUSSAC'S   LAWS.— ATOMIC   THEORY. 

Gases  combine  in  simple  volumetric  proportions — Relations  which  exist 
between  the  volumes  of  gases  and  their  atomic  and  molecular  weights — 
Equal  volumes  of  gases  or  vapors  contain  the  same  number  of  molecules 
— The  molecular  weights  are  equal  to  double  the  densities  compared  to 
hydrogen. 

Among  these  new  facts  it  is  convenient  to  first  notice  those 
which  were  discovered  by  Gay-Lussac,  from  1805  to  1808. 
They  relate  to  the  volumes  of  gases  which  combine  together. 


28 


ELEMENTS    OF    MODERN    CHEMISTRY. 


Experiment. — 10  cubic  centimetres  of  hydrogen  and  5  cubic 
centimetres  of  oxygen  are  introduced  into  a  tube  (Fig.  6),  which 

is  inverted  over  the  mer- 
cury-trough. The  gaseous 
mixture  occupies  the  up- 
per portion  of  the  tube, 
which  is  an  eudiometer. 
Into  the  upper  extremity 
of  this  tube  is  hermeti- 
cally cemented  a  small 
iron  wire  with  a  little 
ball  at  each  extremity. 
Another  iron  wire  passes 
through  the  wall  of  the 
tube  at  a  short  distance 
from  the  upper  extremity, 
in  such  a  manner  that  the 
interior  extremity  of  this 
second  wire  is  opposite, 
and  at  a  short  distance 
from  the  lower  ball  of  the 
superior  and  vertical  wire. 
A  little  iron  chain  is  at- 
tached to  the  exterior  end 
of  the  horizontal  wire,  and 

dips  into  the  mercury  of  the  trough.  Things  being  thus 
arranged,  the  inferior  extremity  of  the  eudiometer  is  closed 
by  an  iron  cap,  and  the  charged  plate  of  an  electrophorus  is 
approached  to  the  upper  button.  A  spark  instantly  passes  be- 
tween the  two  buttons  in  the  eudiometer,  and  a  bright  flash  is 
seen  to  fill  the  whole  space  occupied  by  the  gaseous  mixture. 
The  combination  of  the  two  gases  has  taken  place  with  the 
development  of  luminous  heat.  Water  has  been  formed,  and 
is  condensed  in  drops  too  small  to  be  perceptible.  If  now  the 
eudiometer  be  opened,  by  removing  the  cap  which  closes  it 
under  the  mercury,  the  latter  at  once  rises  to  the  top  of  the 
tube,  and  fills  the  whole  of  the  space  at  first  occupied  by  the 
hydrogen  and  oxygen.  These  gases  have  then  combined  exactly 
in  the  proportion  of  10  volumes  of  the  first  to  5  of  the  second, 
or  more  simply,  in  the  proportion  of  2  volumes  to  1  volume. 

If  the  eudiometer-tube  be  now  surrounded  by  a  wider  glass 
tube,  and  the  latter  be  filled  with  oil  heated  to  120°,  the  heat 


GAY-LUSSAC'S    LAWS. — ATOMIC    THEORY.  29 

communicated  to  the  eudiometer  will  be  sufficient  to  convert 
into  steam  the  water  which  was  condensed,  and  it  may  be 
proved,  all  corrections  being  made,  that  the  vapor  occupies  a 
volume  equal  to  exactly  10  cubic  centimetres  ;  that  is,  a  volume 
equal  to  that  of  the  hydrogen  employed. 

From  the  facts  thus  established  we  draw  the  conclusion  that 
2  volumes  of  hydrogen  exactly  combine  with  1  volume  of 
oxygen  to  form  2  volumes  of  vapor  of  water. 

There  is  thus  determined  a  simple  ratio  not  only  between 
the  volumes  of  hydrogen  and  oxygen  which  combine,  but 
further,  between  the  volume  of  vapor  of  water  formed  and 
the  sum  of  the  volumes  of  the  composing  gases.  3  volumes 
of  the  latter  are  reduced  to  exactly  2  by  the  combination. 

Analogous  facts  have  been  discovered  for  other  gases,  as 
shown  by  the  following  examples : 

2  volumes  of  nitrogen  +  1  volume  of  oxygen  =  2  volumes  of  nitrogen 

monoxide. 
2  volumes  of  chlorine  +  1  volume  of  oxygen  =  2  volumes  of  chlorine 

monoxide. 

In  other  cases  the  combination  of  two  gases  determines  a 
still  greater  contraction,  and  the  initial  volume  is  reduced  one- 
half.  Thus 

1  volume  of  nitrogen  +  3  volumes  of  hydrogen  =  2  volumes  of  ammonia 
gas. 

Finally,  when  two  gases  combine  in  equal  volumes,  their 
combination  usually  takes  place  without  contraction ;  in  other 
words,  the  volume  of  the  gas  produced  is  equal  to  the  sum  of 
the  volumes  of  the  component  gases. 

From  these  collected  facts  we  may  draw  the  following  general 
conclusions : 

1.  There  is  a  simple  relation  between  the  volumes  of  gases 
which  combine. 

2.  There  is  a  simple  relation  between  the  sum  of  the  volumes 
of  the  combining  gases  and  the  volume  of  the  gas  resulting 
from  the  combination. 

These  laws  were  first  signalized  by  Gay-Lussac,  whose  name 
is  attached  to  them.  Their  importance  is  immense ;  they  have 
added  a  notable  development  to  the  atomic  theory. 

If  the  definite  proportions  by  weight  in  which  bodies  com- 
bine represent,  according  to  Dalton,  the  relative  weights  of 
their  atoms,  it  is  natural  to  conclude  that  the  definite  and 
simple  proportions  by  volume  in  which  gases  combine,  accord- 

3* 


30 


ELEMENTS    OF    MODERN    CHEMISTRY. 


ing  to  Gay-Lussac,  represent  the  volumes  occupied  by  the 
atoms.  Under  the  same  volume  gases  would  then  contain 
the  same  number  of  atoms.  This  was  first  proposed  by  Am- 
pere, who  based  his  conclusion  on  the  important  consideration 
that  gases  dilate  and  contract  nearly  equally  when  submitted 
to  the  same  variations  of  temperature  and  pressure.  Within 
certain  limits  the  proposition  is  true  ;  it  applies  to  a  large  num- 
ber of  simple  gases.  But  if  equal  volumes  of  these  gases, 
measured,  let  it  be  well  understood,  under  the  same  conditions 
of  temperature  and  pressure,  contain  the  same  number  of  atoms, 
it  is  evident  that  the  weights  of  these  equal  volumes  should 
represent  the  weights  of  the  atoms.  In  other  words,  the 
atomic  weights  of  the  simple  gases  should  be  proportional  to 
their  densities. 

The  densities  of  gases  and  vapors  represent  the  weights  of 
these  gases  or  vapors  compared  to  the  weight  of  an  equal 
volume  of  air.  To  determine  the  density,  a  certain  volume  of 
the  given  gas  is  weighed,  and  this  weight  is  divided  by  that  of 
an  equal  volume  of  air,  under  the  same  conditions  of  tempera- 
ture and  pressure.  The  air  is  then  the  unit  to  which  are  com- 
pared the  densities  of  gaseous  bodies.  On  comparing  these 
densities  to  that  of  hydrogen,1  which  we  take  as  unity,  we  find 
that  the  same  numbers  express  almost  exactly  the  densities  and 
the  atomic  weights,  the  unit  to  which  the  densities  are  com- 
pared, that  is,  hydrogen,  being  the  same  as  that  to  which  are 
compared  the  atomic  weights.  The  figures  in  the  following 
table  demonstrate  this  to  be  the  case : 


ELEMENTS. 

Densities  of 
Gases  or  Vapors, 
Air  being  Unity. 

Densities, 
Hydrogen  being 
Unity. 

Atomic 
Weights. 

Hydrogen      .     .          .     . 

0  0693 

1 

1 

Oxygen      

1.1056 

15.9 

16 

Nitrogen  
Sulphur  (density  at  1000°) 
Chlorine   

0.9714 
2.22 
2.44 

14 

32 
35.2 

14 
32 
35.5 

5  393 

778 

80 

Iodine  

8.716 

125.8 

127 

1  To  do  this  it  is  sufficient  to  multiply  the  densities  of  the  gases  compared 
to  air  by  -  -  =  14.44,  which  is  the  density  of  the  air  compared  to  hy- 


drogen  as  unity. 


GAY-LUSSAC'S    LAWS. — ATOMIC    THEORY.  31 

It  is  seen  from  this  table  that  if  the  densities  of  gases  be 
compared  to  hydrogen  as  unity,  just  as  the  weights  of  their 
atoms  are  compared  to  hydrogen  as  unity,  the  same  figures,  or 
very  nearly  the  same  figures,  express  both  the  densities  and 
the  atomic  weights.  We  may  add  that,  for  all  the  elements 
taken  in  the  gaseous  state,  there  has  been  determined  between 
the  densities  referred  to  hydrogen  and  the  atomic  weights,  if 
not  equality,  at  least  a  simple  ratio.  These  remarkable  rela- 
tions were  pointed  out  by  (Jay-Lussac. 

Equal  volumes  of  the  simple  gases  above  enumerated  con- 
tain the  same  number  of  atoms.  Two  volumes  of  hydrogen, 
then,  contain  twice  as  many  atoms  as  one  volume  of  oxygen  ; 
and  when  these  gases  combine  in  the  ratio  of  2  volumes  of  the 
first  to  1  of  the  second,  we  must  admit  that  each  atom  of  oxy- 
gen combines  with  2  atoms  of  hydrogen.  We  say,  then,  that 
water  is  composed  of  2  atoms  of  hydrogen  and  1  atom  of  oxy- 
gen. These  three  atoms  so  united  constitute  the  smallest 
quantity  of  water  that  can  exist  in  the  free  state.  This  is 
called  a  molecule  of  water. 

But  what  volume  does  this  molecule  occupy  ?  The  experi- 
ment has  shown  us.  We  have  seen  that  2  volumes  of  hydro- 
gen, in  combining  with  1  volume  of  oxygen,  yield  2  volumes 
of  vapor  of  water.  One  molecule  of  water  in  the  gaseous  state, 
then,  occupies  2  volumes,  if  1  atom  of  hydrogen  occupy  1 
volume,  and  if  1  atom  of  oxygen  occupy  1  volume.  It  is 
seen  that  the  volumes  represent  the  atoms,  and  the  relative 
weights  of  equal  volumes,  that  is,  the  densities,  represent  the 
weights  of  the  atoms. 

Let  us  now  consider  another  compound  gas, — ammonia, — 
composed  of  hydrogen  and  nitrogen.  A  very  simple  experi- 
ment will  show  in  what  proportion  the  atoms  of  these  elements 
are  combined  in  this  gas,  and  the  volume  occupied  by  the 
compound  compared  with  the  volumes  of  its  compopent  gases. 

Experiment. — 100  volumes  of  ammonia  gas  are  introduced 
into  a  tube  inverted  upon  the  mercury-trough  (Fig.  7),  and 
the  walls  of  which  are  pierced  at  the  upper  end  by  two  plati- 
num wires,  between  the  ends  of  which  a  small  space  is  left. 
To  these  wires  are  attached  the  extremities  of  the  two  con- 
ducting wires  of  a  Ruhmkorff  coil,  and  the  current  is  passed 
so  that  a  series  of  electric  sparks  traverses  the  ammonia  between 
the  extremities  of  the  wires  in  the  tube.  The  gas  is  imme- 
diately decomposed,  and  the  level  of  the  mercury  in  the  tube 


32  ELEMENTS    OF    MODERN    CHEMISTRY. 

is  depressed.  When  the  experiment  has  terminated  it  is  found 
that  the  volume  of  the  gas  has  been  doubled.  Instead  of  100 
volumes,  there  are  now  200,  the  gas  being  measured  under  the 
same  conditions  of  temperature  and  pressure  as  before.  It  is 
found,  by  an  analytical  process  that  will  be  indicated  further 
on,  that  these  200  volumes  of  gas  resulting  from  the  decompo- 


FIG.  7. 

sition  of  100  volumes  of  ammonia  are  composed  of  150  vol- 
umes of  hydrogen  and  50  volumes  of  nitrogen.  These  150 
volumes  of  hydrogen  and  50  volumes  of  nitrogen  are  condensed 
by  their  union  into  100  volumes  of  ammonia.  In  other  words, 
3  volumes  of  hydrogen  and  1  volume  of  nitrogen  are  combined 
together  in  2  volumes  of  ammonia.  And  as  the  volumes  rep- 
resent atoms,  it  follows  that  in  ammonia  gas  3  atoms  of  hydro- 
gen are  combined  with  1  atom  of  nitrogen.  But  the  quantity  of 
ammonia  containing  1  atom  of  nitrogen  and  3  atoms  of  hydro- 
gen is  the  smallest  quantity  of  ammonia  that  can  exist.  It  is 
a  molecule  of  ammonia,  and  this  molecule  occupies  2  volumes, 
if  1  atom  of  nitrogen  or  1  atom  of  hydrogen  occupy  1  volume. 

Here,  then,  is  another  compound  gas, — ammonia, — of  which 
the  molecule  occupies  2  volumes,  like  that  of  water.  It  is  the 
same  with  all  the  gases.  All  of  the  atoms  which  are  combined 
to  constitute  the  molecule  of  a  gas  or  vapor  are  so  condensed 
that  the  molecule  occupies  the  same  volume  as  the  molecule  of 
vapor  of  water,  or  the  molecule  of  ammonia. 

We  may  state,  then,  with  the  Italian  chemist,  Avogadro, 
that  equal  volumes  of  gases  contain  the  same  number  of  mole- 
cules, and  that  each  of  these  molecules  occupies  2  volumes, 
if  1  atom  of  hydrogen  occupy  1  volume.  It  follows  that 
the  weight  of  2  volumes  of  a  compound  gas  represents  the 
weight  of  its  molecule,  the  weight  of  one  volume  of  hydrogen 


GAY-LUSSAC'S   LAWS.  —  ATOMIC   THEORY.  33 

being  1.  But  the  weight  of  2  volumes  of  a  gas  or  vapor  is 
nothing  more  than  the  double  of  its  density  compared  to  hy- 
drogen ;  for  the  density  is  the  weight  of  1  volume  compared 
with  the  weight  of  1  volume  of  hydrogen.  To  find  the  weight 
of  the  molecule  (the  weight  of  2  volumes)  of  a  gas  or  vapor, 
it  is  then  only  necessary  to  multiply  its  density  compared  to 
hydrogen  (the  weight  of  1  volume)  by  2. 

The  densities  of  gases  and  vapors  are  generally  referred  to 
air  as  unity.  To  bring  them  to  the  hydrogen  standard,  they 
are  multiplied  by  the  number  expressing  the  relation  of  the 
density  of  hydrogen  to  that  of  air,  which  is  -o.-oVoT  —  14.44. 
The  product  thus  obtained  expresses  the  density  compared  to 
hydrogen,  that  is,  the  weight  of  1  volume.  To  find  the  weight 
of  2  volumes,  or  the  molecular  weight,  it  is  then  only  necessary 
to  multiply  the  densities  compared  to  air  by  twice  the  ratio  of 
the  density  of  the  air  compared  to  hydrogen,  that  is,  by  the 
constant  factor,  — 


0.0693        0.0693 


28  88. 


It  is  seen  that  if  the  atomic  weights  of  certain  gases  can  be 
deduced  from  a  comparison  of  their  densities,  this  same  physi- 
cal notion  may  also  serve  for  the  determination  of  the  molecu- 
lar weights  of  compound  gases. 

The  numbers  which  represent  double  the  densities  of  gases 
or  vapors  compared  to  hydrogen,  express  also  the  molecular 
weights  of  these  gases  or  vapors,  that  is,  the  weight  of  all 
the  atoms  in  the  molecule,  the  weight  of  one  atom  of  hydrogen 
being  1. 

Considering  the  examples  already  given,  we  may  deduce  the 
molecular  weights  of  water  and  of  ammonia  from  the  densities 
of  steam  and  ammonia  gas. 

The  density  of  vapor  of  water,  determined  by  Gay  -Lussac- 
is  0.6235.  To  find  the  molecular  weight  of  water,  it  is  suffi- 
cient to  multiply  this  figure  by  28.88.  The  product,  18,  ex- 
presses the  weight  of  a  molecule  of  water,  which  is  indeed 
composed  of 

2  atoms  of  hydrogen  .......     =2 

1  atom  of  oxygen        .......     =16 

1  molecule  of  water     .......     =18 

Sir  Humphry  Davy  found  for  the  density  of  ammonia  the 
B* 


34  ELEMENTS    OF    MODERN    CHEMISTRY. 

number  0.5901.  This  being  multiplied  by  28.88,  the  product, 
17.04,  should  represent  the  weight  of  one  molecule  of  am- 
monia. Ammonia  contains 

3  atoms  of  hydrogen        .......       3 

1  atom  of  nitrogen 14 

1  molecule  of  ammonia 17 

The  discovery  of  the  laws  which  govern  the  combination  of 
gases  by  volume  has  seconded  in  the  most  efficacious  manner 
the  progress  of  the  atomic  theory. 

In  the  first  place,  it  has  established  a  marked  distinction  be- 
tween the  old  idea  of  equivalents  and  the  modern  one  of  atoms. 
The  equivalents  represented  merely  the  ponderable  proportions 
according  to  which  bodies  combine  ;  the  atomic -weights  repre- 
sent the  relative  weights  of  the  volumes  of  gases  which  com- 
bine. The  equivalent  of  hydrogen — unity — expressed  merely 
that  hydrogen  was  the  unit  to  which  were  referred  the  weights 
of  other  bodies  with  which  it  entered  into  combination.  The 
atomic  weight  of  hydrogen  is  the  weight  of  one  volume  of 
hydrogen,  taken  as  unity,  and  to  this  unit  are  referred  the 
atomic  weights  of  other  bodies. 

In  the  second  place,  the  discovery  of  Gay-Lussac  has  shown 
how  the  atomic  weights  of  simple  bodies  and  the  molecular 
weights  of  compound  bodies  can  be  determined  from  the  den- 
sities of  gases  and  vapors. 

However,  this  resource  would  be  insufficient  in  very  many 
cases.  It  only  applies  to  gaseous  bodies,  or  such  as  can  be 
conveniently  converted  into  vapor.  Now,  there  are  many  sub- 
stances with  which  this  is  impossible,  and  serious  difficulties 
would  be  encountered  in  the  determination  of  the  atomic 
weights  of  certain  elements  were  it  not  for  another  physical 
law,  discovered  by  two  French  physicists,  Dulong  and  Petit. 
It  denotes  the  relations  which  exist  between  the  specific  heats 
and  the  atomic  weights. 

LAW   OF   SPECIFIC    HEATS. 

It  is  known  that  in  order  to  raise  the  temperatures  of  differ- 
ent bodies  through  the  same  number  of  thermometric  degrees 
very  different  amounts  of  heat  are  required.  Thus,  one  kilo- 
gramme of  water  requires  30  times  more  heat  than  one  kilo- 
gramme of  mercury  to  raise  its  temperature  one  degree,  and 
if  the  quantity  of  heat  required  to  raise  the  temperature  of 


LAW    OF    SPECIFIC    HEATS. 


35 


one  kilogramme  of  water  one  degree  be  represented  by  1,  the 
quantity  required  to  raise  the  same  weight  of  mercury  one 
degree  will  be  represented  by  0.0333  =  -j^.  This  fraction  ex- 
presses the  specific  heat  of  mercury  between  0  and  100°. 

The  specific  heat  of  a  solid  or  liquid  body  is  then  the  amount 
of  heat  required  to  raise  the  temperature  of  a  certain  weight  of 
the  body  one  degree,  the  amount  required  to  raise  the  tempera- 
ture of  an  equal  weight  of  water  one  degree  being  taken  as 
unity. 

In  1820,  Dulong  and  Petit  discovered  the  remarkable  fact 
that  if  the  figures  which  express  the  atomic  weights  of  the 
elements,  liquid  or  solid,  be  multiplied  by  those  which  express 
their  specific  heats,  the  product  obtained  is  sensibly  constant ; 
in  other  words,  the  specific  heats  of  the  elements  are  inversely 
as  their  atomic  weights.  It  results  that  if  such  quantities  of 
the  elements  be  taken  as  represent  their  atomic  weights,  the 
amount  of  heat  required  to  raise  the  temperature  of  each  one 
degree  will  be  sensibly  the  same.  The  law  discovered  by  Du- 
long and  Petit  may  then  be  expressed, — the  atoms  of  the  solid 
elements  possess  sensibly  tfte  same  specific  lieats. 

This  law  permits  the  deduction  of  the  atomic  weights  from 
the  specific  heats.  Indeed,  it  is  evident  that  if  the  product  of 
the  specific  heats  by  the  atomic  weights  be  a  constant,  that 
may  be  called  the  atomic  heat,  dividing  this  product  by  the 
specific  heat  should  give  the  atomic  weight.  The  product 
which  represents  the  atomic  heat  is  6.4,  very  nearly,  as  may  be 
seen  from  the  following  table  : 


Products  of  the 

NAMES  OF  THE  SOLID  ELEMENTS. 

Specific 
Heats. 

Atomic 
Weights. 

Specific  Heats 
by  the  Atomic 
Weights. 

Atomic  Heats. 

Sulphur,  between  0  and  100°   .     . 

0.2026 

32 

6.483 

Selenium  

0  0762 

79  5 

6  058 

Tellurium      

0.0474 

129 

6  115 

Bromine,  between  —78  and  —20° 

0.0843 

80 

6.744 

Iodine,  between  0  and  100°     .     . 

0.0541 

127 

6.873 

Phosphorus,  between  +  1  and  30° 

0.1887 

31 

5.850 

0  0814 

75 

6  105 

Carbon,  diamond,  at  600°    .     .     . 

0.46 

12 

5.52 

Boron,  crystallized,  at  600°      .     . 

0.5 

11 

5.5 

Silicon   at  1000°               .... 

0  20? 

28 

5  66 

Potassium           

0  1695 

39.1 

6  500 

36  ELEMENTS    OP   MODERN    CHEMISTRY. 

TABLE.— Continued. 


NAMES  OF  THE  SOLIJ>  ELEMENTS. 

Specific 
Heats. 

Atomic 
Weights. 

Products  of  the 
Specific  Heats 
l>y  the  Atomic 
Weights. 
Atomic  Heats. 

Sodium,  between  —34  and  +  7°  . 
Lithium    ...          

0.2934 
0  9408 

23 

7 

6.748 
6  586 

Thallium  

0  03355 

204 

6  844 

Magnesium   ...          ... 

0  2499 

24 

5  998 

Aluminium    

0  2143 

27 

5  786 

0  1217 

65 

6  693 

Iron      

0  0110 

56 

6  116 

0  09555 

65  2 

6  230 

0  05669 

112 

6  349 

Cobalt  

0  1068 

59 

6.301 

Nickel  

0  1089 

59 

6  424 

Tungsten  

0  0334 

184 

6  146 

0  0722 

96 

6.931 

0  0314 

207 

6  499 

0  0308 

210 

6.468 

0  09515 

63.5 

6.042 

0  05077 

122 

6.193 

Tin  

0  05623 

118 

6.635 

Mercury,  between  —  77.5  and  —  44° 
Silver   

0.03247 
0.05701 

200 
108 

6.494 
6.157 

Gold 

0  0324 

197 

6.383 

Platinum       

0  03293 

197.5 

6.503 

0.0593 

106.5 

6.315 

0  03063 

199.2 

6.101 

Rhodium  . 

0  05803 

104.4 

6.058 

0.03259 

198 

6.452 

Carbon,  silicon,  and  boron  have  long  been  regarded  as  ex- 
ceptions to  Dulong  and  Petit's  law.  Their  specific  heats  had 
been  determined  at  comparatively  low  temperatures,  and  the 
products  of  the  numbers  obtained  by  the  atomic  weights  fell 
much  below  6.4.  These  exceptions  have  disappeared  ;  the  ex- 
periments of  M.  Weber  have  shown  that  the  specific  heat  of 
carbon,  silicon,  and  boron  increases  with  the  temperature,  and 
that  for  the  first  two  elements  it  attains  a  limit,  where  it  re- 
mains sensibly  constant.  The  figures  given  in  the  preceding 
table  for  these  three  elements  are  those  of  M.  Weber,  and  it  is 
seen  that  on  multiplying  them  by  the  respective  atomic  weights 
of  carbon,  silicon,  and  boron,  values  are  obtained  which  are 
sensibly  near  6.4. 

It  will  otherwise  be  remarked  that  there  are  sensible  differ- 


ISOMORPHISM. — CHEMICAL    NOMENCLATURE,  ETC.         37 

ences  between  the  numbers  expressing  the  atomic  heats  of  the 
various  solid  elements,  showing  that  Dulong  and  Petit's  law, 
although  true  in  its  generality  and  striking  in  its  enunciation, 
is  not  free  from  certain  perturbations  which  give  to  it  the 
character  of  an  approximate  law.  It  is  the  same  with  other 
physical  laws,  Mariotte's  law,  for  example. 


ISOMORPHISM. 

While  considering  the  atomic  theory  and  the  determination 
of  the  relative  weights  of  the  ultimate  particles  of  bodies,  we 
cannot  pass  in  silence  a  discovery  which  has  had  a  great  influ- 
ence upon  the  development  of  that  theory.  It  is  due  to  E. 
Mitscherlich,  who,  in  1819,  made  known  the  law  of  isomor- 
phism. This  law  may  be  thus  stated :  there  is  such  a  relation 
between  the  atomic  constitutions  of  compound  bodies  belonging 
to  the  same  group  and  their  crystalline  form,  that  "  the  same 
number  of  atoms  combined  in  the  same  manner  produce  the 
same  crystalline  form,  the  latter  being  independent  of  the 
chemical  nature  of  the  atoms,  and  determined  solely  by 
their  number  and  arrangement."  The  importance  of  the 
proposition  as  regards  the  atomic  structure  of  bodies  is  self- 
evident.  We  will  reconsider  it  when  treating  of  the  general 
characteristics  of  salts,  but  we  may  remark  here  that  it  has 
been  of  great  value  in  the  determination  of  certain  atomic 
weights.  Indeed,  in  some  cases  considerations  of  a  chemical 
nature  cannot  decide  between  two  numbers  for  the  atomic 
weight  of  a  given  element.  The  choice  is  then  determined  by 
the  following  considerations :  such  a  value  must  be  attributed 
to  the  atomic  weight  that  the  isomorphous  compounds  formed 
by  the  element  and  by  another  to  which  it  is  analogous,  may 
be  represented  by  similar  atomic  formula. 


CHEMICAL    NOMENCLATURE   AND    NOTATION. 

GENERAL  CONSIDERATIONS. — Sixty-four  substances  are  now 
known  which  can  be  resolved  into  no  simpler  forms  of  matter, 
and  which  are  consequently  considered  as  simple  bodies  or  ele- 
ments. By  combining  together,  they  form  an  innumerable  mul- 
titude of  compound  bodies  containing  two  or  more  elements. 

4 


38  ELEMENTS    OF    MODERN    CHEMISTRY. 

In  order  to  distinguish  these  bodies  from  each  other  it  is  neces- 
sary to  give  a  name  to  each,  for  each  constitutes  a  distinct  sub- 
stance. 

The  names  of  the  simple  bodies  have  been  chosen  at  will, 
and  in  some  cases  recall  some  peculiar  property  of  the  sub- 
stances designated.  It  was  formerly  the  same  with  compound 
bodies ;  there  was  no  definite  rule  for  their  nomenclature. 
From  this  there  resulted  a  great  complication  of  words  which 
embarrassed  the  exposition  of  ideas,  and  often  for  the  same  sub- 
stance there  were  a  number  of  synonyms,  of  which  the  least 
inconvenience  was  to  uselessly  fatigue  the  memory.  Hence 
chemists  have  felt  the  necessity  of  a  regular  nomenclature, 
applicable  to  compound  bodies,  and  capable  of  indicating  their 
composition.  Such  is  the  principle  of  the  chemical  nomen- 
clature suggested  by  Guyton  de  Morveau,  and  developed  by 
Lavoisier,  Berthollet,  and  Fourcroy.  This  nomenclature,  with 
some  modifications,  introduced  by  the  progress  of  the  science, 
is  still  adopted. 

Independently  of  this  language,  the  rules  of  which  will 
presently  be  detailed,  chemists  have  adopted  a  written  nota- 
tion which  expresses  in  concise  form  the  atomic  constitution 
of  compounds.  The  name  of  each  element  is  represented  by 
a  symbol,  which  also  expresses  one  atom  t)f  the  substance. 
This  symbol  is  the  initial  letter  of  the  name  of  the  element, 
or  the  initial  letter  with  another  when  the  names  of  two  ele- 
ments begin  with  the  same  letter.  Thus,  H  represents  one 
atom  of  hydrogen  weighing  1  ;  0  represents  one  atom  of 
oxygen  weighing  16.  By  combining  these  symbols  together, 
it  is  easy  to  represent  in  a  precise  manner  the  atomic  compo- 
sition of  compound  bodies.  From  such  combinations  result 
chemical  formulas,  the  use  of  which  was  introduced  into  the 
science  by  Berzelius. 

In  the  following  table  will  be  seen  the  names  of  the  ele- 
ments now  known,  together  with  their  atomic  weights,  and  the 
symbols  by  which  the  atoms  of  the  elements  are  represented  in 
the  notation. 

The  greater  number  of  the  elements  possess  certain  physi- 
cal properties  which  characterize  them  as  metals.  They  are 
opaque,  and  possess  a  peculiar  lustre,  which  does  not  disappear 
under  the  burnisher.  They  are  good  conductors  of  heat  and 
electricity. 


CHEMICAL    NOMENCLATURE    AND    NOTATION. 


39 


NAMES  OF  THE  ELE- 
MENTS. 

1 

Atomic 
Weights. 

NAMES  OF  THE  ELE- 
MENTS. 

Symbols. 

Atomic 
Weiglits. 

Aluminium  .     .     . 

Al 

27.5 

Mercury    (hydrar- 

Antimony     (stibi- 

gyrum)     .     .     . 

Hg 

200 

um) 

Sb 

122 

Molybdenum 

Mo 

96 

Arsenic    .... 

As 

75 

Nickel      .... 

Ni 

59 

Barium     .... 

Ba 

137 

Niobium  .... 

Nb 

94 

Bismuth  .... 

Bi 

210 

Nitrogen  .... 

N 

14 

Boron 

Bo 

11 

Osmium   .... 

Os 

199.2 

Bromine  .... 

Br 

80 

Oxygen    .... 

0 

16 

Cadmium      .     . 

Cd 

112 

Palladium     .     . 

Pd 

106.6 

Caesium    .... 

Cs 

133 

Phosphorus  .     .     . 

P 

31 

Calcium    .... 

Ca 

40 

Platinum       .     .     . 

Pt 

197.5 

Carbon      .... 

C 

12 

Potassium  (kalium) 

K 

39.1 

Cerium     .... 

Ce 

92 

Rhodium  .... 

Rh 

104.4 

Chlorine  .... 

Cl 

35.5 

Rubidium     .     .     . 

Rb 

85.2 

Chromium    . 

Cr 

52.5 

Ruthenium  .     .     . 

Ru 

104.4 

Cobalt      .... 

Co 

59 

Selenium  .... 

Se 

79.5 

Copper      .... 

Cu 

63.5 

Silicon      .... 

Si 

28 

Didytniuin    . 

Di 

96 

Silver    (argentum) 

Ag 

108 

Erbium    .... 

Er 

112.6 

Sodium    (natrium) 

Na 

23 

Fluorine  .... 

Fl 

19 

Strontium     .     .     . 

Sr 

87.5 

Gallium   .... 

Ga 

69.9 

Sulphur    .... 

S 

32 

Glucinium    .     .     . 

Gl 

9.5 

Tantalium     .     .     . 

Ta 

182 

Gold  (auruin)    .     . 

Au 

197 

Tellurium     .     .     . 

Te 

128 

Hydrogen     .     .     . 

H 

1 

Thallium.     .     .     . 

Tl 

204 

Indium     .... 

In 

113.4 

Thorium  .... 

Th 

234 

Iodine      .... 

I 

127 

Tin  (stannum)  .     . 

Sn 

118 

Iridium    .... 

Ir 

198 

Titanium      .     .     . 

Ti 

50 

Iron  (ferrum)    .     . 

Fe 

56 

Tungsten    (wolfra- 

Lnnthanium      .     . 

La 

92 

mium    .... 

W 

184 

Lead  (plumbum)  . 

Pb 

207 

Uranium  .... 

Ur 

120 

Lithium   .... 

Li 

7 

Vanadium    .     .     . 

V 

51.37 

Magnesium  .     .     . 

Mg 

24 

Yttrium    .... 

Y 

89.6 

Manganese  . 

Mn 

55 

Zinc     

Zn 

65.2 

Zirconium     .     .     . 

1 

Zr 

90 

Other  elements,  fewer  in  number,  do  not  possess  these  prop- 
erties. They  have  been  called  the  non-metallic  bodies,  some- 
times the  metalloids.  They  include  the  following : 


HYDROGEN.  OXYGEN. 


NITROGEN. 


SULPHUR.  PHOSPHORUS. 

CHLORINE.  SELENIUM.  ARSENIC. 

BROMINE.          TELLURIUM.  ANTIMONY. 

IODINE.  (BISMUTH  ?) 
FLUORINE. 


SILICON. 
CARBON. 


From  a  theoretic  stand-point  this  distinction  presents  but 


40  ELEMENTS    OF    MODERN    CHEMISTRY. 

little  value,  for  it  is  impossible  to  draw  an  exact  line  sepa- 
rating the  metals  from  the  non-metallic  bodies. 

NOMENCLATURE  OF  COMPOUND  BODIES. — The  principle  of 
chemical  nomenclature  is  to  indicate  the  composition  of  com- 
pound bodies  by  their  names.  Among  such  compounds  the 
most  numerous  and  the  most  important  are  those  containing 
oxygen.  They  are  binary  or  ternary ;  that  is,  the  oxygen  in 
them  is  combined  with  one  or  two  other  elements. 

Binary  Oxygen  Compounds. — We  will  first  consider  the 
more  simple  oxidized  bodies,  those  which  result  from  the  com- 
bination of  oxygen  with  but  one  other  element,  metallic  or 
non-metallic.  These  compounds  are  called  oxides,  and  differ 
as  the  element  associated  with  the  oxygen  is  metallic  or  non- 
metallic.  In  combining  with  non-metallic  elements,  oxygen 
generally  forms  compounds  which  are  the  anhydrides  of  acids, 
that  is,  compounds  capable  of  uniting  with  water  to  form 
acids ;  with  the  metals  it  forms  metallic  oxides. 

Experiments. — 1.  A  small  piece  of  phosphorus  is  placed  in 
a  capsule  floating  on  the  surface  of  mercury.  It  is  ignited 
and  the  capsule  covered  with  a  bell-jar  (Fig.  8).  The  phos- 
phorus burns,  giving  off  a  thick  smoke,  which  condenses  in 


FIG.  8. 


white  flakes  on  the  sides  of  the  bell-jar.  This  substance  re- 
sults from  the  combination  of  the  phosphorus  with  the  oxygen 
of  the  air :  it  is  phosphorus  pentoxide,  or  phosphoric  anhydride. 


CHEMICAL    NOMENCLATURE   AND    NOTATION.  41 

2.  If  lead  be  heated  in  the  air  and  maintained  for  some 
time  in  a  state  of  fusion,  its  brilliant  surface  becomes  tarnished 
and  covered  with  grayish  particles,  which  are  finally  converted 
into  a  yellow  powder.  This  body  is  formed  by  the  combina- 
tion of  the  lead  with  oxygen :  it  is  plumbic  oxide,  or  oxide  of 
lead. 

But,  as  we  have  seen,  such  combination  can  take  place  in 
different  proportions.  An  atom  of  a  body  may  unite  with 
1,  2,  3,  or  more  atoms  of  oxygen,  and  the  names  of  the  com- 
pounds so  formed  should  indicate  the  degree  of  oxidation. 

Sulphur  forms  two  compounds  with  oxygen :  one  contains  2 
atoms  of  oxygen  to  1  atom  of  sulphur ;  the  other,  3  atoms  of 
oxygen  to  1  of  sulphur.  They  are  designated  by  the  names 
sulphurcws  oxide,  or  anhydride,  and  sulphuric  oxide,  or  anhy- 
dride. 

The  written  notation  represents  them  by  the  symbols 

SO2, 

so3; 

which  express  their  atomic  compositions.  The  number  of 
atoms  of  any  element  is  indicated  by  a  small  figure  placed  after 
and  a  little  above  or  below  the  symbol  of  that  element. 

The  degree  of  oxidation  is  then  expressed  by  the  termina- 
tion in  ous  or  ic  of  the  name  of  the  other  element,  which 
indicates  the  kind  of  oxide,  ic  denoting  the  superior  oxide. 

Mercury  forms  two  compounds  with  oxygen.  The  first 
contains  2  atoms  of  mercury  for  1  of  oxygen ;  the  second,  1 
atom  of  mercury  to  1  of  oxygen.  They  are  designated  by  the 
names  and  symbols  as  follows : 

Mercurous  oxide Hg'20. 

Mercuric  oxide HgO. 

The  names  monoxide,  sesquioxide,  dioxide,  etc.,  as  will  be 
seen  further  on,  are  also  employed.1 

A  monoxide  is  a  combination  of  1  atom  of  metal  with  1  atom  of  oxygen. 
A  sesquioxide  "  "  2  atoms  "  "  3  atoms  " 

A  dioxide  "  "  1  atom         "         "       2       "  « 

It  is  easy  then  to  understand  the  signification  of  the  follow- 
ing names  and  symbols : 

1  The  prefixes  proto,  biordeut,  and  ter  have  been,  and  are  yet,  frequently 
employed  instead  of  mono,  di,  and  tri. 

4* 


42  ELEMENTS   OP    MODERN    CHEMISTRY. 

Manganese  monoxide MnO. 

Manganese  sesquioxide Mn2Os. 

Manganese  dioxide MnO2. 

The  oxide  most  rich  in  oxygen  is  sometimes  called  the  per- 
oxide. 

Oxygen  Acids  and  Metallic  Hydrates. — The  oxygen  com- 
pounds that  we  have  just  considered  may  unite  with  the  ele- 
ments of  water  to  form  more  complex  compounds,  which  are 
ternary,  that  is,  they  contain  three  elements.  To  the  two  ele- 
ments of  the  oxide  is  then  added  a  third,  independently  of  the 
oxygen  of  the  water,  that  is,  its  hydrogen. 

The  oxygen  acids  usually  result  from  the  union  of  water 
with  the  non-metallic  oxides. 

Experiment.  —  Sulphur  trioxide  or  sulphuric  anhydride 
occurs  in  white  silky  tufts.  It  is  very  volatile,  and  if  a  bottle 
containing  it  be  opened,  its  vapor  comes  in  contact  with  the 
moist  air  and  forms  thick  white  fumes.  If  a  small  quantity  of 
this  substance  be  thrown  into  water,  it  immediately  disappears 
and  combines  with  that  liquid.  So  great  is  the  energy  of  the 
reaction  that  the  heat  disengaged  gives  rise  to  the  production 
of  steam,  which,  being  suddenly  formed  and  condensed  in  the 
midst  of  the  cooler  liquid  mass,  causes  a  peculiar  noise,  a  sort  of 
hissing.  When  the  sulphuric  oxide  is  dissolved  in  the  water, 
the  solution  presents  a  very  acid  reaction.  It  contains  sulphuric 
acid,  the  compound  long  known  under  the  name  of  oil  of  vitriol. 

This  reaction  may  be  represented  in  the  abbreviated  lan- 
guage of  the  notation,  which  expresses  the  atomic  composition 
of  bodies  with  so  much  precision.  The  formula  of  sulphuric 
anhydride  or  sulphur  trioxide  is 

SO3; 
that  of  water  is 

H20. 

Then  if  sulphuric  acid  result  from  the  addition  of  all  of  the 
elements  of  water  to  those  of  sulphuric  trioxide,  it  should  contain 

SO3  -f  H20  ==  H2S04. 

This  is  a  chemical  equation,  and  it  is  seen  that  the  two 
terms  of  the  first  member  express  the  atomic  composition  of 
the  reacting  bodies,  while  the  single  term  of  the  second  mem- 
ber gives  the  atomic  composition  of  the  product  of  the  reac- 
tion. Such  an  equation  accounts  for  all  of  the  atoms,  and 


CHEMICAL    NOMENCLATURE   AND   NOTATION.  43 

the  sum  of  all  of  the  atoms  written  in  the  first  member  must 
exactly  balance  the  sum  of  all  those  written  in  the  second. 

There  is  a  compound  known  as  nitric  anhydride,  or  nitrogen 
pentoxide.  It  results  from  the  combination  of  nitrogen  with 
oxygen,  and  its  atomic  composition  is  represented  by  the 
formula  N205.  In  combinin  with  water  it  forms  nitric  acid. 


_|_       H20      =       2(HN03). 

Nitric  anhydride.  Water.  Nitric  acid. 

(1  molecule.)  (2  molecules.) 

These  examples,  which  could  be  indefinitely  multiplied,  give 
an  idea  of  the  constitution  of  the  ternary  oxygen  acids.  The 
rules  which  have  been  already  given  for  the  nomenclature  of 
the  oxides  apply  also  to  the  nomenclature  of  the  acids.  We 
have  phosphorous  acid  and  phosphoric  acid.  .H^po-phosphor- 
ous  acid  is  an  acid  of  phosphorus  containing  still  less  oxygen 
than  phosphorous  acid.  (Hypo,  literally,  under.) 

The  metallic  hydrates  result  from  the  combination  of  water 
with  the  metallic  oxides.  It  is  well  known  that  when  quick- 
lime is  sprinkled  with  water  it  becomes  heated,  increases  in 
volume,  cracks  into  pieces,  and  is  finally  converted  into  a  white, 
impalpable  powder,  which  constitutes  slaked  lime,  —  a  com- 
pound of  the  lime  with  water.  Lime  is  the  oxide  of  a  metal 
called  calcium.  In  combining  with  water  it  forms  a  ternary 
compound  of  calcium,  hydrogen,  and  oxygen  ;  this  is  hydrate 
of  calcium,  or,  as  it  is  commonly  called,  hydrate  of  lime. 

CaO     -f     H20     =     CaH202. 

Calcium  oxide.          Water.  Calcium  hydrate. 

(Lime.) 

The  metal  potassium,  the  radical  of  potash,  forms  with  oxy- 
gen a  compound  which  contains  two  atoms  of  potassium  com- 
bined with  one  atom  of  oxygen.  The  composition  of  this  body 
is  then  represented  by  the  formula  K2O. 

It  combines  with  water  with  great  energy,  and  forms  with  it 
potassium  hydrate  or  caustic  potassa. 

K2O     +      H20     ==     2KOH. 

Potassium  oxide.         Water.          Potassium  hydrate. 
(2  molecules.) 

Oxygen  Salts.—  The  oxygen  salts  result  from  the  action  of 
the  oxygen  acids  upon  the  oxides  or  upon  the  metallic  hydrates. 

Experiment.  —  The  formation  of  a  gait  may  be  illustrated  by 
a  modification  of  one  of  the  experiments  already  described. 

A  quantity  of  dilute  nitric  acid  is  slightly  reddened  by  a  so- 


44  ELEMENTS   OF   MODERN   CHEMISTRY. 

lution  of  blue  litmus  or  syrup  of  violets.1  Some  dilute  solution 
of  caustic  potassa  is  also  treated  with  the  same  coloring  matter ; 
the  syrup  of  violets  will  assume  a  green  color,  or  blue  litmus 
will  remain  unchanged. 

The  latter  liquid,  which  is  alkaline,  is  now  added  drop  by 
drop  to  the  acid,  until  the  red  color  disappears,  giving  place  to 
the  violet  color  of  the  syrup  of  violets  or  the  blue  of  the  litmus. 
The  liquid  is  now  neutral.  It  contains  neither  free  nitric  acid 
nor  free  potassa.  Both  have  disappeared  as  such ;  they  are 
reciprocally  neutralized,  the  first  having  lost  its  acid  taste,  the 
second  its  extreme  caustic  properties.  They  have  produced  a 
body  having  a  saline,  cooling  taste,  and  exerting  no  action  upon 
vegetable  colors.  It  is  a  neutral  salt  which  has  been  formed. 
It  is  called  potassium  nitrate.  It  is  the  nitre  or  saltpetre  of 
the  ancient  chemists.  It  is  not,  however,  the  sole  product  of 
the  reaction.  Water  is  formed  at  the  same  time,  and  if  we 
would  comprehend  the  entire  phenomenon,  the  reaction  will  be 
expressed  by  the  following  equation  : 

HNO3     -f     KOH      =      KNO3     +     H20. 

Nitric  acid.      Potassium  hydrate.  Potassium  nitrate.          Water. 

It  is  seen  that  the  salt,  potassium  nitrate,  is  a  ternary  com- 
pound, similar  in  constitution  to  nitric  acid  itself.  On  com- 
paring the  two  formulae, 

HNO3  nitric  acid, 
KNO3  potassium  nitrate, 

it  is  seen  that  they  only  differ  by  the  K  in  the  second  occupy- 
ing the  place  held  by  the  H  in  the  first.  It  may  then  be  said 
that  potassium  nitrate  represents  in  a  manner  nitric  acid  in 
which  the  hydrogen  has  been  replaced  by  an  equivalent  quan- 
tity of  potassium.  This  definition  applies  to  the  entire  class 
of  compounds  under  consideration.  A  salt  represents  an  acid 
of  which  the  hydrogen  has  been  wholly  or  partially  replaced 
by  an  equivalent  quantity  of  metal. 

The  acids  constitute  the  salts  of  hydrogen :  they  are  neu- 
tralized when  this  hydrogen  is  replaced  by  a  metal.  The  acid 
or  hydrogen  salt  differs  from  the  metallic  salt.  From  a  theoretic 
point  of  view,  an  acid  is  a  compound  of  the  same  order  as  a 
salt,  and  if  these  bodies  are  separated  by  such  great  differences 

1  An  infusion  of  common  purple  cabbage  may  be  substituted  for  syrup 
of  violets. 


CHEMICAL   NOMENCLATURE   AND    NOTATION.  45 

of  properties,  this  is  due  to  the  nature  of  the  base.  What 
a  difference,  indeed,  between  hydrogen  gas  and  the  metals ! 

We  have  studied  the  formation  of  a  salt  by  the  action  of  an  acid, 
nitric  acid,  upon  a  metallic  hydrate,  potassium  hydrate.  The 
anhydrous  oxides  may  also  form  salts  by  reacting  with  the  acids. 

Experiment. — Yellow  oxide  of  lead,  when  digested  with 
dilute  sulphuric  acid,  is  converted  into  a  white,  insoluble  pow- 
der, which  is  lead  sulphate.  This  is  a  salt,  but  it  is  not  the  only 
product  of  the  reaction,  for  water  is  formed  at  the  same  time. 
H2SO  +  PbO  =  PbSO4  +  H20. 

Sulphuric  acid.        Lead  oxide.        Lead  sulphate.  Water. 

Lastly,  among  other  modes  of  formation  of  salts,  there  is  one 
which  is  worthy  of  interest,  and  of  which  an  idea  may  be  ob- 
tained from  the  following  example. 

Sulphur  trioxide,  or  sulphuric  anhydride,  combines  energetic- 
ally with  barium  oxide  or  baryta,  and  from  the  union  of  all  of 
the  elements  of  both  compounds  there  results  a  salt, — barium 
sulphate. 

SO3      4-       BaO     =     BaO,S03  or  BaSO4. 

Sulphur  trioxide.    Barium  oxide.  Barium  sulphate. 

But,  whether  this  salt  be  formed  under  these  conditions,  or 
by  the  action  of  sulphuric  acid,  its  composition  only  differs 
from  that  of  the  latter  acid  by  the  substitution  of  Ba  for  H2. 
H2S04  sulphuric  acid,  hydrogen  sulphate, 
BaSO*  barium  sulphate. 

The  reactions  which  we  have  just  studied,  and  which  indicate 
the  principal  methods  of  the  formation  of  salts,  are  sufficient  to 
make  clear  the  definition  before  given,  that  salts  are  derived  from 
acids  by  the  substitution  of  a  metal  for  hydrogen.  The  nomen- 
clature defines  and  preserves  these  relations.  To  distinguish  the 
different  salts  of  the  same  acid,  the  name  of  the  metal  is  placed 
first,  and  this  is  followed  by  the  name  of  the  acid,  which  is  but 
slightly  changed, — ic  is  changed  to  ate,  and  ous  to  ite. 

Thus  Sulphuric  acid  gives  sulphates. 

Nitric  acid  "  nitrates. 

Perchloric  acid  "  perchlorates. 

Sulphurous  acid  "  sulphites. 

Hyposulphurous  acid     "  hyposulphites. 

These  generic  names  follow  the  names  of  the  metals  which 
enter  into  the  composition  of  the  salts,  and  which  specify  them, 
as  it  were.  Thus,  we  have  : 


46  ELEMENTS    OP    MODERN    CHEMISTRY. 

Potassium  sulphate,  copper  sulphate,  lead  sulphate,  etc. ; 

Sodium  sulphite ; 

Potassium  nitrate,  barium  nitrate,  silver  nitrate,  etc. 

But  we  know  that  a  single  metal  may  form  several  com- 
pounds with  oxygen.  In  reacting  upon  the  same  acid  these 
different  oxides  give  rise  to  the  formation  of  different  salts. 

Thus,  two  different  sulphates  of  copper  are  obtained,  as  sul- 
phuric acid  is  caused  to  react  with  cuprous  oxide,  or  with 
cupric  oxide. 

H-'SO*    +     Cu20     =     Cu2SO*     -f     IPO. 

Sulphuric  acid.        Cuprous  oxide.        Cuprous  sulphate.         Water. 

H-'SO     +      CuO     =      CuSO4     +     IPO. 

Cupric  oxide.         Cupric  sulphate. 

It  is  easy  to  distinguish  these  two  salts  from  each  other  by 
using  the  adjectives  cuprous  and  cupr-ic  before  the  substantive 
sulphate.  Thus,  we  have  mercuroits  and  mercuric  sulphates  ; 
ferrous  and  ferric  sulphates. 

The  preceding  considerations  will  give  an  idea,  sufficient  for 
the  time  being,  of  the  constitution  and  the  nomenclature  of 
salts.  Their  further  exposition  will  be  completed  farther  on. 

Nomenclature  of  Non-Oxygenized  Compounds. — The  non- 
metallic  elements  other  than  oxygen  can  combine  among  them- 
selves or  with  the  metals.  Such  compounds  are  designated  by 
the  name  of  one  of  the  elements  followed  by  the  abbreviated 
name  of  the  other  terminating  in  ide.  Thus,  the  compounds 
of  the  metals  with  chlorine,  bromine,  iodine,  sulphur,  arsenic, 
and  carbon  are  called  chlorides,  brom/cfes,  iodides,  sulph/c^es, 
arsenides,  carbides.  We  thus  have  sodium  chloride,  potassium 
bromide,  lead  iodide,  zinc  arsenide,  iron  carbide.  The  termi- 
nation uret  was  formerly  used  in  place  of  ide. 

But  a  non-metallic  body,  such  as  chlorine  or  sulphur,  can, 
like  oxygen,  form  several  compounds  with  the  same  metal.  In 
these  compounds  1  atom  of  metal  may  be  united  with  1  or  2 
atoms  of  sulphur,  or  with  1,  3,  or  5  atoms  of  chlorine,  or  again 
with  2  or  4  atoms  of  chlorine.  Such  atomic  composition  is 
expressed  by  the  following  names  and  symbols : 

Iron  wjoHosulphide FeS. 

Iron  bisulphide FeS2. 

Phosphorus  fn'chloride PCI3. 

Phosphorus  ^Htachloride PCI5. 

Tin  tftchloride SnCl2. 

Tin  teJrachloride •  ...  SnCl*. 

Antimony  fn'chloride SbCl3. 

Antimony  joen/achloride SbCl5. 


CHEMICAL    NOMENCLATURE   AND    NOTATION.  47 

The  names  thus  express  precisely  the  number  of  atoms  of 
the  second  element  in  combination  with  1  atom  of  the  first. 

The  compounds  of  chlorine,  bromine,  iodine,  and  several 
other  elements  with  hydrogen  are  acids  ;  they  readily  exchange 
their  hydrogen  for  a  metal,  so  forming  compounds  that  are 
analogous  to  the  oxygen  salts,  and  which  constitute  the  haloid 
salts  of  Berzelius. 

Experiment. — The  compound  of  chlorine  with  hydrogen  is 
hydrochloric  acid  ;  it  is  a  gas,  and  dissolves  in  water,  forming 
a  fuming,  strongly-acid  liquid.  When  it  is  carefully  poured 
into  a  concentrated  solution  of  caustic  potassa  there  appears  a 
white  precipitate,  formed  of  little  crystals  and  presenting  the 
appearance  of  a  salt.  This  is  potassium  chloride.  It  is  formed 
according  to  the  following  reaction,  and  its  formation  is  at- 
tended by  the  production  of  heat : 

HC1     +     KOH    =    KC1     +     H20. 

Hydrochloric  Potassium  Potassium  Water, 

acid.  hydrate.  chloride. 

The  hydrogen  compounds  of  bromine,  iodine,  fluorine,  sul- 
phur, etc.,  possess  analogous  properties.  They  are  called 

Hydrobroraic  acid HBr. 

Hydriodic  acid        HI. 

Hydrofluoric  acid HF1. 

Sulphydric  acid  or  sulphuretted  hydrogen  .     .     .  H2S. 

The  chlorides  may  combine  among  themselves.  It  is  the 
same  with  the  bromides,  iodides,  sulphides,  etc.  If  a  solution 
of  potassium  chloride  be  poured  into  a  concentrated  solution 
of  platinic  chloride,  a  yellow  precipitate,  constituting  a  com- 
pound of  the  two  chlorides,  is  formed.  It  is  the  double  chlo- 
ride of  platinum  and  potassium,  or  potassium  platino-chloride. 

There  exist,  likewise,  double  sulphides  formed  by  the  union 
of  two  simple  sulphides.  Such  compounds  constitute  what  are 
called  sulphur  salts. 

Alloys  and  Amalgams. — The  compounds  of  the  metals 
with  each  other  are  called  alloys.  Amalgams  are  the  alloys 
of  mercury,  that  is,  the  compounds  of  this  liquid  metal  with 
another  metal. 


48 


ELEMENTS   OF   MODERN   CHEMISTRY. 


HYDROGEN. 

Density  compared  to  air 0.0693. 

Atomic  weight  (1  volume  taken  as  unity)  H  =  1. 

This  body  was  discovered  in  1*766  by  Cavendish.  It  is  one 
of  the  elements  of  water,  hence  its  name,  which  was  given  by 
Lavoisier. 

Experiments. — 1.  A  small  piece  of  sodium  is  passed  under  a 
tube  filled  with  mercury  and  inverted 
on  the  mercury-trough ;  it  rises  to 
the  top  of  the  jar,  and  some  water 
is  then  introduced  (Fig.  9).  As  soon 
as  the  water  touches  the  sodium  a 
brisk  disengagement  of  gas  is  ob- 
served ;  this  is  hydrogen,  produced  by 
the  decomposition  of  the  water,  and 
the  reaction  by  which  it  is  set  at 
liberty  is  expressed  in  the  following 
equation : 

2H20  +  Na2  =  2NaOH  +    H2. 

FlO.  9.  Water.        Sodium.  Sodium          Hydrogen. 

hydrate. 

If  the  tube  be  now  inverted  and  a  lighted  taper  be  rapidly 
brought  to  the  orifice,  the  gas  will  burn  with  a  pale  flame.  A 
piece  of  reddened  litmus-paper  plunged  into  the  water  con- 
tained in  the  tube  has  its  blue  color  at  once  restored,  and 
this  change  is  produced  by  the  sodium  hydrate  or  caustic  soda 
dissolved  in  the  water. 

2.  Some  thin  sheet-zinc  cut  into  small  pieces  is  introduced 
into  a  rather  large  test-jar  (Fig.  10),  and  some  hydrochloric 
acid  is  then  poured  upon  it.  A  rapid  eifervescence  imme- 
diately takes  place,  and  if  a  lighted  taper  be  brought  to  the 
mouth  of  the  jar,  the  stream  of  hydrogen  evolved  takes  fire. 
This  hydrogen  is  produced  by  the  decomposition  of  the  hydro- 
chloric acid  by  the  zinc,  which  is  converted  into  chloride. 


2HC1     +     Zn 

Hydrochloric  Zinc. 

acid. 
(2  molecules.) 


ZnCP     +     H2. 

Zinc  Hydrogen, 

chloride. 


HYDROGEN. 


49 


Preparation. — A  reaction  analogous  to  the  preceding  is 
turned  to  advantage  for  the  preparation  of  large  quantities  of 
hydrogen.  Dilute 
sulphuric  acid  is  de- 
composed by  zinc. 

A  two-necked  bot- 
tle is  about  half  filled 
with  water,  and  gran- 
ulated zinc,  or  sheet- 
zinc  cut  into  small 
pieces,  is  introduced; 
sulphuric  acid  is  then 
added  in  small  quan- 
tities by  the  aid  of 
a  funnel-tube  which 
dips  under  the  surface 
of  the  water  (Fig. 
11).  The  reaction  at 
once  commences,  and 
hydrogen  is  disen- 
gaged. When  the 
air  at  first  contained 
in  the  bottle  has  been 
entirely  expelled,  the 
gas  may  be  collected 
in  jars  or  bottles  filled 
with  water  and  in- 
verted on  the  pneu- 
matic trough. 

In  this  reaction  the  zinc  disappears  and  dissolves  in  the 
liquid  with  evolution  of  heat,  and  it  often  happens,  if  the  liquid 
be  sufficiently  concentrated,  that  colorless  crystals  of  zinc 
sulphate  are  formed  on  cooling.  This  salt  and  hydrogen  are 
the  sole  products  of  the  reaction  of  pure  zinc  upon  sulphuric 
acid  largely  diluted  with  water. 

H2S04     +     Zn     =     ZnSO*     +     H2. 

Sulphuric  acid.  Zinc.  Zinc  sulphate.       Hydrogen. 

Physical  Properties. — Hydrogen  is  a  colorless  gas,  and 
when  pure  has  neither  taste  nor  odor.  It  is  the  lightest  of  all 
known  bodies,  its  density  compared  to  air  being  0.0693 ;  that 
is,  if  one  volume  of  air  weigh  1,  one  volume  of  hydrogen, 
measured  under  the  same  conditions  of  temperature  and  pres- 
c  5 


FIG.  io. 


50 


ELEMENTS    OF    MODERN    CHEMISTRY. 


sure,  weighs    only  0.0693.      Hydrogen  is  then    14.44  time 
The  weight  of  one  litre  of  hydrogen  at  0° 


lighter  than  air. 


FiG.  11. 

and  under  the  normal  pressure  is  0.0895  gramme.  Instead 
of  comparing  the  densities  of  gases  and  vapors  to  that  of  air, 
it  is  preferable  to  compare  them  to  that  of  hydrogen  taken  as 
unity  (page  30). 

Hydrogen  passes  with  great  facility  through  vegetable  and 
animal  membranes,  and  through  porous  substances  that  are  im- 
pervious to  water.  It  cannot  be  kept  in  a  glass  vessel  that 
presents  the  least  crack,  for  it  would  pass  through  much  more 
readily  than  air.  This  property  is  expressed  by  saying  that  hy- 
drogen is  very  diffusible.  According  to  Magnus,  it  is  the  only 
gas  gifted  with  an  appreciable  conductibility  for  heat ;  in  this 
respect  it  is  related  to  the  metals.  From  a  consideration  of  its 
physical  properties  and  its  combined  chemical  properties,  Fara- 
day long  ago  announced  the  metallic  character  of  hydrogen. 

This  theoretic  prediction  has  recently  received  a  remarkable 
confirmation.  Hydrogen,  which  was  long  regarded  as  incoerci- 
ble,  has  been  liquefied  and  even  solidified.  Cailletet,  of  Paris, 
obtained  it  in  the  form  of  a  cloud  by  exposing  it  to  a  pressure 
of  300  atmospheres  at  a  temperature  of  — 29°  and  then  sud- 
denly relieving  the  pressure.  Raoul  Pictet,  of  Geneva,  has 
advanced  still  further.  By  an  apparatus  of  incomparable 
power,  he  subjected  it  to  a  temperature  of  — 140°  under  a 
pressure  of  650  atmospheres.  Under  these  circumstances,  hy- 
drogen was  liquefied,  and  was  visible  as  a  steel-blue,  liquid  jet 


HYDROGEN.  51 

at  the  moment  of  its  projection  from  the  tube  in  which  it  was 
condensed.  The  cold  produced  by  its  passage  from  the  liquid 
to  the  gaseous  state  was  so  great  that  a  portion  of  the  liquid  was 
solidified,  and  fell  to  the  ground  in  metallic  grains,  producing 
a  shrill  sound  as  it  struck  the  floor.  Another  portion  of  the 
solidified  hydrogen  remained  in  the  tube  during  several  minutes. 

Among  the  physical  properties  of  hydrogen  may  be  men- 
tioned the  remarkable  faculty  it  possesses  of  passing  through 
plates  of  iron  or  platinum  at  high  temperatures  (H.  Sainte- 
Claire  Deville  and  Troost).  It  is  well  known  that  it  rapidly 
passes  through  thin  sheets  of  caoutchouc.  According  to 
Graham,  this  property  is  related  to  that  possessed  by  certain 
solid  bodies,  and  particularly  metals,  such  as  iron,  platinum, 
and  palladium,  of  absorbing  hydrogen  gas.  This  chemist 
designated  the  phenomenon  by  the  name,  occlusion  of  hydro- 
gen by  the  metals.  Palladium  especially  is  distinguished  by 
the  energy  with  which  it  absorbs  hydrogen.  It  can  condense 
in  its  pores  nine  hundred  times  its  own  volume  of  the  gas.  A 
palladium  wire  may  be  charged  with  hydrogen  by  arranging  it  in 
a  voltameter  so  that  it  constitutes  the  negative  pole  of  a  small 
battery,  the  positive  pole  being  a  stout  platinum  wire.  When 
the  current  passes,  the  hydrogen  set  at  liberty  at  the  negative 
pole  (see  page  71)  is  condensed  in  the  palladium.  This  metal 
undergoes  at  the  same  time  a  remarkable  change.  Its  volume 
augments  and  its  density  diminishes,  but  its  metallic  lustre 
remains,  as  do  also,  to  a  certain  degree,  its  tenacity  and  con- 
ductibility  for  electricity ;  besides  this  it  becomes  magnetic. 
There  is  thus  formed  a  sort  of  alloy  of  palladium  and  hydro- 
gen, containing  about  20  volumes  of  palladium  to  1  volume  of 
hydrogen  reduced  to  the  solid  state.  The  density  of  this  solid 
hydrogen  compared  to  that  of  water,  according  to  the  determi- 
nations of  Troost  and  Hautefeuille,  is  0.62  :  it  is  a  little  greater 
than  that  of  lithium.  Graham  insisted  upon  the  metallic  char- 
acter of  hydrogen  thus  alloyed  with  palladium,  and  proposed 
for  it  the  name  hydrogenium. 

Chemical  Properties.—  Hydrogen  is  a  combustible  gas,  and 
the  product  of  its  combustion  is  water. 

Experiments. — 1 .  A  lighted  taper  may  be  thrust  into  a  rather 
wide  tube  filled  with  hydrogen  (Fig.  14).  The  gas  takes  fire 
on  contact  with  the  flame,  but  the  taper  is  extinguished  in  the 
atmosphere  of  hydrogen.  It  may  be  relighted  by  withdrawing 
it  through  the  burning  gas.  The  experiment  shows  at  the 


52 


ELEMENTS    OF    MODERN    CHEMISTRY. 


same  time  that  hydrogen  is  inflammable  and  that  it  is  incapa- 
ble of  supporting  combustion  itself. 

2.  A  gas-bottle,  A  (Fig.  12),  is  arranged  for  the  preparation 
of  hydrogen,  and  water,  zinc,  and  sulphuric  acid  are  intro- 

0 


FIG.  12. 

duced.  The  hydrogen  evolved  is  made  to  traverse  the  tube 
CB,  which  is  filled  with  fragments  of  chloride  of  calcium  ;  after 
having  been  dried  by  this  substance,  which  is  very  avid  of 

water,  the  gas  escapes  by  the  tube 
a,  the  end  of  which  is  drawn  out 
to  a  point.  The  jet  of  gas  is 
lighted,  and  burns  with  a  pale 
flame.  A  bell-jar,  D,  is  now 
held  over  the  burning  jet,  and 
the  sides  of  the  glass  soon  be- 
come covered  with  dew,  the 
drops  of  which  unite  and  run 
down  to  the  edge  of  the  j  ar.  This 
is  water,  and  it  is  formed  by  the 
combustion  of  the  hydrogen  ;  that 
is,  by  its  combination  with  the 
oxygen  of  the  air. 

3.  A  jet  of  hydrogen  may  be 
lighted  by  holding  in  it  a  tuft  of 
asbestos  which  has  been  dipped 
in  platinum  black,  that  is,  finely-divided  platinum.  The  con- 
densation of  the  hydrogen  in  the  pores  of  the  finely-divided 
metal  is  so  rapid  that  the  platinum  becomes  heated  to  redness, 
and  then  ignites  the  gas. 


FIG.  13. 


HYDROGEN. 


53 


4.  A  tube  filled  with  hydrogen  may  be  held  in  the  vertical 
position,  bottom  upwards,  without  the  gas  escaping  rapidly  by 
the  inferior  opening.     If  the  tube  be  inclined,  the  hydrogen 
overflows  and  escapes  upwards  through  the  air.     It  may  then 
be  received  in  a  second  tube  held  vertically  above  the  first, 
which  is  inclined  more  and  more  (Fig.  13).     The  passage  of 
the  gas  into  the  upper  tube  can  be  demonstrated  by  approach- 
ing to  the  latter  a  lighted  taper,  when  the  hydrogen  will  burn 
with  a  faint  explosion. 

Before  igniting  or  collecting  hydrogen  escaping  from  a  gen- 
erator, it  should  always  be  ascertained  that  the  whole  of  the  air 
has  been  expelled,  otherwise  dangerous  explosions  may  result. 

5.  The  explosions  may  take  place  with  the  production  of  a 
harmonious  sound,  if  they  are  made  to  succeed  each  other 


Fia.  14. 


Fia.  15. 


rapidly  and  at  regular  intervals.  These  conditions  are  realized 
by  burning  a  small  jet  of  hydrogen  in  a  somewhat  large  tube 
(Fig.  15).  The  flame  is  drawn  away  from  the  jet  by  the  draft 
in  the  tube,  but  immediately  recedes  as  the  ascending  hydro- 


54 


ELEMENTS    OF    MODERN    CHEMISTRY. 


gen  gas  mixes  with  the  air,  at  the  same  time  producing  a  faint 
explosion,  and  the  rapid  succession  of  these  explosions  produces 
a  musical  tone. 

The  hydrogen  condensed  in  palladium  appears  to  have  some 
chemical  properties  different  from  those  of  gaseous  hydrogen 
(Graham).  It  combines  in  the  dark  and  at  ordinary  tempera- 
tures with  iodine  and  chlorine ;  the  direct  union  of  ordinary 
hydrogen  with  iodine  is  impossible,  and  with  chlorine  it  takes 
place  at  the  common  temperature  only  under  the  influence  of 
light.  It  seems,  then,  that  hydrogen,  when  associated  with 
palladium,  is  more  active  than  in  the  ordinary  state. 


OXYGEN. 

Density  compared  to  air 1.1056. 

Density  compared  to  hydrogen 16. 

Atomic  weight  0 =16. 

Oxygen  was  discovered,  in  1I7'74,  by  Priestley,  who  obtained 

it  by  heating  red 
precipitate  or 
mercuric  oxide. 

Experim  ent. — 
A  tube,  a  (Fig. 
16),  contains  a 
concentrated  so- 
'lution  of  the  dis- 
infecting powder 
known  as  chlo- 
ride of  lime ;  a 
small  quantity 
of  the  peroxide 
of  cobalt,  a  com- 
pound of  oxygen 
with  the  metal 
cobalt,  is  then 
introduced,  and 
the  whole  is  gen- 
tly heated.  A 
brisk  efferves- 

Fm    1G  cence  takes  place, 

and  if  a  match 
which  has  been  just  blown  out  and  still  presents  a  spark  of  fire 


OXYGEN.  55 

be  thrust  into  the  mouth  of  the  tube,  it  is  instantly  relighted, 
and  burns  with  great  brilliancy.  This  effect  is  due  to  a  gas 
which  is  being  disengaged,  and  which,  to  use  the  expression  of 
Lavoisier,  is  eminently  fitted  to  support  combustion. 

It  is  the  gas  to  which  that  great  chemist  gave  the  name 
oxygen.  It  is  produced  by  a  very  simple  reaction.  Under 
the  influence  of  the  peroxide  of  cobalt,  the  calcium  hypochlorite 
which  is  contained  in  the  chloride  of  lime  is  converted  into 
calcium  chloride  and  oxygen. 

CaCPO2       =       CaCP       +       O2. 

Calcium  hypochlorite.      Calcium  chloride.  Oxygen. 

Preparation. — Large  quantities  of  oxygen  may  be  prepared 
by  a  process  analogous  to  the  preceding.  When  potassium 
chlorate  is  heated,  it  is  converted  into  potassium  chloride,  and 
gives  up  all  of  its  oxygen.  To  facilitate  this  decomposition,  a 
small  quantity  of  manganese  dioxide  is  mixed  with  the  chlo- 
rate. The  part  taken  by  the  manganese  dioxide  is  analogous 
to  that  of  the  cobalt  peroxide  in  the  preceding  reaction,  and  is 
not  thoroughly  understood  ;  it  is  most  probable  that  it  serves 
to  distribute  the  heat  more  regularly  through  the  mass  of 
chlorate.  If  the  temperature  be  sufficiently  elevated,  the  de- 
composition of  the  chlorate  is  complete,  and  takes  place  accord- 
ing to  the  following  equation  ; 

KCK)3  KC1        +        O3. 

Potassium  chlorate.        Potassium  chloride.  Oxygen. 

The  operation  may  be  conducted  in  a  glass  retort,  which 
should  be  about  one-third  filled  with  the  mixture  of  chlorate 
and  dioxide  ;  to  the  beak  of  the  retort  is  adapted  a  delivery- 
tube,  which  dips  under  the  surface  of  the  water  or  mercury  in 
the  trough  (Fig.  17).  The  retort  is  then  heated  by  an  alco- 
hol or  gas  lamp,  and  the  chlorate  melts  and  disengages  its  oxy- 
gen with  effervescence.  Towards  the  close  of  the  operation, 
the  heat  is  increased  in  order  to  decompose  into  potassium 
chloride  and  oxygen  any  potassium  perchlorate  that  may  have 
been  formed  by  the  union  of  a  portion  of  the  evolved  oxygen 
with  some  of  the  chlorate. 

To  make  larger  quantities  of  oxygen  for  filling  the  gas- 
holders of  laboratories,  etc.,  a  mixture  of  potassium  chlorate 
and  manganese  dioxide  is  heated  in  a  sheet-iron  or  copper  retort. 

At  a  bright  red  heat  manganese  dioxide  gives  up  a  third 


56  ELEMENTS   OP   MODERN   CHEMISTRY. 

of  its  oxygen,  and  is  converted  into  the  red  oxide  of  manga- 
nese. 

3Mn02  Mn304          +  O2. 

Manganese  dioxide.  Red  oxide  of  manganese.  Oxygen. 

Oxygen  can  be  cheaply  manufactured  on  the  large  scale  by 
the  process  of  Tessie  du  Mottay.  This  depends  upon  the  for- 
mation of  sodium  manganate  by  the  action  of  air  upon  a  heated 


FIG.  17. 

mixture  of  manganese  dioxide  and  caustic  soda,  and  the  subse- 
quent decomposition  of  this  manganate  at  about  450°  by  a 
current  of  steam,  a  decomposition  which  again  sets  at  liberty 
the  oxygen  absorbed  by  the  manganese  dioxide  to  form  sodium 
manganate.  The  operation  is  continuous. 

Physical  Properties. — Oxygen  is  a  colorless,  odorless,  taste- 
less gas ;  it  is  a  little  heavier  than  the  air.  If  one  volume  of 
hydrogen  weighs  1,  the  same  volume  of  oxygen,  measured 
under  the  same  conditions  of  temperature  and  pressure,  weighs 
16.  This  is  expressed  by  saying  that  the  density  of  oxygen 
compared  to  that  of  hydrogen  is  16.  A  litre  of  oxygen  weighs 
1.437  gr.  at  0°  and  under  the  normal  pressure. 

Until  lately  oxygen  had  been  considered  as  a  permanent  gas. 
By  subjecting  it  to  a  pressure  of  300  atmospheres  and  a  tem- 
perature of  — 29°,  and  then  suddenly  relieving  the  pressure, 
Cailletet  obtained  it  in  the  form  of  a  cloud.  Raoul  Pictet 
liquefied  it  by  a  pressure  of  300  atmospheres  and  a  temperature 


OXYGEN. 


57 


of  — 140°.  He  attributes  to  liquid  oxygen  a  density  near  that 
of  water,— about  0.9787. 

Oxygen  is  but  slightly  soluble  in  water.  A  litre  of  water 
dissolves  0.041  litre,  or  41  cubic  centimetres,  at  0° ;  0.032  litre 
at  10° ;  0.028  litre  at  20°.  The  fractions  0.041,  0.032,  0.028, 
represent  the  coefficients  of  solubility  of  oxygen  in  water  at 
the  temperatures  of  0°,  10°,  and  20°. 

Chemical  Properties. — Oxygen  combines  directly  with  most 
of  the  other  elements,  and  the  union  often  takes  place  with 
such  energy  that  there  results  a  great  evolution  of  luminous 
heat :  it  gives  rise  to  the  phenomenon  of  combustion. 

Experiments. — A  cone  of  charcoal  of  which  the  point  is  red- 
hot  is  plunged  into  a  globe  filled  with  oxygen  (Fig.  18),  and 
immediately  combustion  takes  place  with  great  brilliancy.  The 
oxygen  combines  with  the  carbon,  forming  a  colorless  gas,  which 
is  carbonic  acid  gas. 

In  like  manner,  sulphur  and  phosphorus  burn  in  oxygen,  the 
first  producing  a  colorless,  irritating  gas  known  as  sulphurous 


FIG.  18. 


FIG.  19. 


acid  gas,  the  second  emitting  thick  fumes,  which  condense  in 
white  flakes  of  phosphoric  oxide. 

A  watch-spring  may  be  drawn  out  into  a  spiral,  and  a  small 
piece  of  tinder  attached  to  one  end ;  after  igniting  the  tinder, 
the  spiral  is  rapidly  plunged  into  a  bell-jar  filled 'with  oxygen, 
and  resting  upon  a  plate  containing  a  layer  of  water  (Fig.  19). 
The  tinder  burns  energetically,  and  heats  the  end  of  the  spiral 
to  redness ;  then  the  combustion  of  the  iron  itself  commences, 
and  goes  on  with  unparalleled  brilliancy,  and  a  production  of 
c* 


58  ELEMENTS    OP    MODERN    CHEMISTRY. 

heat  so  intense  that  the  oxide  of  iron  formed  melts  and  falls 
in  incandescent  drops,  which  fuse  themselves  into  the  sur- 
face of  the  plate,  even  after  having  traversed  the  layer  of 
water. 

In  the  same  manner,  the  combustion  of  the  metal  magnesium 
may  be  effected  in  oxygen  ;  it  takes  place  with  dazzling  splen- 
dor, and  gives  rise  to  the  production  of  a  white  powder,  which 
is  magnesia,  or  magnesium  oxide. 

The  preceding  experiments  are  examples  of  rapid  combus- 
tion. We  have  seen  that  solid  substances,  such  as  charcoal, 
iron,  and  magnesium,  become  incandescent  in  combining  with 
oxygen  :  it  is  the  phenomenon  of  fire.  We  have  also  seen  that 
vapors,  like  those  of  sulphur  and  phosphorus,  become  lumi- 
nous in  their  combination  with  oxygen :  this  is  the  phenome- 
non of  flame. 

But  fire  and  flame  are  not  necessary  concomitants  of  the 
union  of  bodies  with  oxygen.  It  is  true  that  such  union  is 
always  accompanied  by  the  production  of  heat ;  but  often  this 
heat  is  not  luminous ;  sometimes  it  is  imperceptible  to  our 
senses. 

Thus  iron,  the  combination  of  which  with  oxygen  at  a  red 
heat  gives  rise  to  such  a  brilliant  combustion,  may  unite  with 
this  gas  at  ordinary  temperatures  under  the  influence  of 
moisture.  There  is  thus  formed  ferric  hydrate,  which  consti- 
tutes rust. 

This  oxidation  of  the  iron,  which  takes  place  slowly,  pro- 
duces a  feeble  disengagement  of  heat,  which  is,  however,  imme- 
diately dissipated.  Such  phenomena  of  oxidation  are  designated 
by  the  name  slow  combustion. 

The  term  combustion  would  then  be  synonymous  with  oxi- 
dation did  we  not  know,  on  the  other  hand,  that  all  chemical 
combination  gives  rise  to  the  production  of  heat.  If  copper 
be  thrown  into  boiling  sulphur,  a  vivid  incandescence  is  pro- 
duced, due  to  the  union  of  the  two  bodies.  Likewise  antimony 
and  arsenic,  when  projected  in  fine  powder  into  an  atmosphere 
of  chlorine,  unite  with  the  latter  body,  producing  a  brilliant 
combustion.  It  is  seen  that  in  these  cases  the  production  of 
luminous  heat  indicates  an  energetic  combination,  but  not  an 
oxidation. 

Oxygen  is  one  of  the  elements  of  the  air ;  it  is  the  cause 
and  the  agent  of  all  combustion,  of  all  oxidation  which  takes 
place  in  our  atmosphere ;  and  the  oxygen  fixes  itself  upon 


OXYGEN.  59 

burning  bodies  in  such  a  manner  that  the  product  of  the  com- 
bustion contains  all  of  the  matter  of  the  combustible  body  and 
all  of  the  matter  of  the  oxygen.  This  is  one  of  the  fundamental 
truths  of  chemistry,  and  for  its  discovery  not  less  than  a  cen- 
tury and  a  half  of  work  was  required.  The  glory  of  the  dis- 
covery belongs  to  Lavoisier. 

His  researches  on  combustion  revealed  to  him  the  true 
nature  of  the  phenomena  of  respiration.  The  respiration  of 
animals  is  a  slow  combustion ;  it  is  the  source  of  animal  heat. 
It  gives  rise  to  the  formation  of  carbonic  acid  gas  and  water, 
products  of  the  complete  oxidation  through  which  must  pass 
those  organic  matters  in  the  economy  which  no  longer  serve 
the  purposes  of  life,  and  all  of  which  contain  carbon  and  hy- 
drogen. 

The  production  of  carbonic  acid  gas  by  the  act  of  respira- 
tion is  easy  to  prove.  It  is  only  necessary  to  blow,  by  the  aid 
of  a  tube,  the  air  contained  in  the  lungs  through  clear  lime- 
water,  which  soon  becomes  milky  from  the  formation  of  insolu- 
ble carbonate  of  lime. 

An  annular  jet  of  hydrogen  through  which  a  jet  of  oxygen 
is  forced  constitutes  what  is  known  as  the  oxyhydrogen  blow- 
pipe, and  is  one  of  the  most  intense  sources  of  heat  known. 
Platinum  melts  before  it  like  wax,  and  iron  and  other  combus- 
tible metals  burn  brilliantly  when  introduced  into  its  flame. 
The  flame  of  the  oxyhydrogen  blowpipe  gives  but  little  light, 
but  when  it  is  projected  upon  a  piece  of  lime,  the  latter  becomes 
heated  to  dazzling  incandescence,  constituting  the  Drummond 
or  calcium  light. 

OZONE,  OR  OXYGEN  PEROXIDE. 
OO2. 

The  repeated  discharges  of  a  good  electric  machine  develop 
a  peculiar  odor.  This  is  due  to  the  production  of  a  body  which 
was  discovered  by  Schbnbein  in  1840,  and  which  he  named 
ozone  (from  o£o>,  I  smell). 

Experiment. — Some  potassium  permanganate  is  mixed  with 
barium  dioxide  in  a  mortar,  the  mixture  transferred  to  a  flask, 
and  moistened  with  sulphuric  acid.  The  characteristic  odor  of 
ozone  immediately  becomes  perceptible,  and  a  moistened  paper, 
impregnated  with  potassium  iodide  and  starch  and  held  in  the 


60 


ELEMENTS    OF    MODERN    CHEMISTRY. 


neck  of  the  flask,  immediately  assumes  a  blue  color.1    This  effect 
is  caused  by  the  ozone  evolved. 

This  remarkable  body  is  also  formed  under  the  following 
circumstances. 

1 .  By  the  passage  of  electric  sparks  through  oxygen. — It  is 
sufficient  to  pass  a  series  of  electric  sparks  through  oxygen 

contained  in  a  tube  above  a  solu- 
tion of  iodide  of  potassium  and 
starch,  in  order  to  produce  the 
blue  color  caused  by  the  ozone 
(Fig.  20). 

It  has  been  noticed  that  the 
largest  quantity  of  ozone  is  pro- 
duced when  the  passage  of  the 
electricity  through  oxygen  is  ef- 
fected, not  by  sparks,  but  by  non- 
luminous  or  obscure  discharges 
(Andrews  and  Tait,  de  Babo). 
Dry  and  pure  oxygen  can  be  con- 
verted into  ozone  in  this  manner. 
But  this  conversion  only  takes 
place  partially,  the  ozone  formed 
remaining  mixed  with  a  large 
excess  of  oxygen.  A  contraction 
takes  place  at  the  moment  the 
oxygen  is  transformed  into  ozone. 
These  experiments  prove  that 
ozone  is  condensed  oxygen  (Andrews  and  Tait,  de  Babo,  Soret). 

2.  By  the  electrolysis  of  water. — When    acidulated  water 
is  decomposed  by  the  battery  current,  the  oxygen  which  is 
disengaged  at  the  positive  pole  contains  small  quantities  of 
ozone,  and  the  proportion  of  the  latter  may  be  increased  by 
adding  a  considerable  quantity  of  sulphuric  or  chromic  acid  to 
the  water. 

3.  During  slow  oxidation. — Some  sticks  of  cleanly-scraped 

1  Such  a  paper  is  called  ozonoscopic.  It  is  colored  blue  by  the  combina- 
tion of  the  starch  with  the  iodine  set  at  liberty  by  the  ozone.  According 
to  Houzeau,  it  is  preferable  to  use  a  delicate,  wine-colored  litmus-paper, 
one-half  of  which  is  impregnated  with  potassium  iodide.  Ozone  will  change 
the  color  of  this  half  to  blue,  for,  in  decomposing  the  potassium  iodide,  it 
forms  potassium  hydrate,  and  this  restores  the  blue  color  to  the  litmus. 
Under  these  conditions,  the  other  half  of  the  paper  undergoes  no  change 
in  color,  while  it  would  be  colored  red  by  acid  vapors,  or  blue  by  ammonia. 


FIG.  20. 


OZONE. 


61 


phosphorus  are  introduced  into  a  bottle  containing  enough 
water  to  just  about  half  immerse  them,  and  the  whole  is  agi- 
tated from  time  to  time.  In  a  short  time  the  air  in  the  bottle 
will  be  charged  with  a  small  quantity  of  ozone. 

According  to  Schonbein,  who  observed  these  facts,  ozone  is 
produced  during  all  slow  combustions.  Thus,  when  oil  of  tur- 
pentine is  exposed  to  the  air  under  the  influence  of  sunlight, 
it  is  slowly  oxidized,  and  in  becoming  resinified,  it  becomes  at 
the  same  time  charged  with  a  small  quantity  of  ozone,  which 
dissolves  in  it. 

4.  JBy  the  decomposition  of  barium  dioxide  by  sulphuric 
acid. — This  decomposition  gives  rise  to  barium  sulphate  and 
oxygen  charged  with  a  small  quantity  of  ozone  (Houzeau). 


H*S04 


BaO2     =     BaSO*     +     H20     +     0 


The  barium  dioxide  is  introduced  in  small  portions  into  sul- 
phuric acid  contained  in  a  flask,  to  the  neck  of  which  is  fitted 
a  glass  stopper  pierced  for  the  passage  of  the  delivery-tube, 
which  is  ground  in  (Fig.  21). 


FIG.  21. 

Properties  of  Ozone. — Ozone  possesses  an  intense  and  pecu- 
liar odor.  At  a  temperature  of  290°  it  is  reconverted  into 
ordinary  oxygen,  the  volume  of  which  is  greater  than  that 
occupied  by  the  ozone.  It  is  then  certainly  condensed  oxygen. 
It  has  energetic  oxidizing  properties ;  it  even  oxidizes  bodies 
which  possess  only  feeble  affinities  for  oxygen.  In  the  presence 
of  alkalies  it  combines  with  nitrogen,  converting  it  into  nitric 
acid,  which  combines  with  the  alkali. 

It  oxidizes  silver  at  ordinary  temperatures,  converting  it  into 

6 


62  ELEMENTS    OF    MODERN    CHEMISTRY. 

the  dioxide  Ag202.  It  instantly  decomposes  potassium  iodide, 
setting  free  the  iodine.  It  is  insoluble  in  water,  but  is  entirely 
soluble  in  oil  of  turpentine  and  oil  of  cinnamon,  both  of  which 
it  slowly  oxidizes.  It  oxidizes  and  destroys  the  greater  number 
of  organic  substances.  In  most  of  these  oxidations  only  a  third 
part  of  the  oxygen  contained  in  ozone  is  active  ;  the  other  two- 
thirds  become  free  in  the  form  of  ordinary  oxygen,  so  that  the 
volume  of  the  latter  set  free  is  exactly  equal  to  that  primitively 
occupied  by  the  ozone. 

Hence  it  is  concluded  that  3  volumes  of  oxygen  are  con- 
densed into  2  volumes  by  their  conversion  into  ozone,  and  if 
ordinary  oxygen  be  the  oxide  of  oxygen  00,  ozone  will  be  oxy- 
gen peroxide  OO2  (Odling). 

00  =  2  volumes  of  oxygen. 

0 

OO2  or  /  \  =  2  volumes  of  ozone. 
0—0 

This  conclusion  of  Odling's  concerning  the  nature  of  ozone, 
has  been  verified  by  the  determination  of  the  density  of  this 
body.  Soret  has  established  that  when  ozone  diluted  with  oxy- 
gen is  absorbed  by  oil  of  turpentine  or  oil  of  cinnamon,  there 
is  a  diminution  of  volume  sensibly  double  the  increase  of 
volume  noticed  on  subjecting  the  same  gas  to  the  action  of 
heat.  He  naturally  concludes  that  the  density  of  ozone  is  one 
and  a  half  times  that  of  oxygen,  or  1.658.  These  figures  have 
been  confirmed  by  direct  experiments  upon  the  rapidity  of 
diffusion  of  ozone.  It  has  been  shown  by  the  researches  of 
Graham  that  when  diffusion  between  two  gases  takes  place 
through  an  opening,  without  the  interposition  of  a  diaphragm, 
the  rapidity  of  diffusion  is  inversely  as  the  square  roots  of  the 
densities  of  the  gases.  Soret  has  demonstrated  that  the 
rapidity  of  diffusion  of  ozone  is  notably  greater  than  that  of 
chlorine,  and  very  near  but  somewhat  less  than  that  of  car- 
bonic acid.  It  results  that  its  density  is  less  than  that  of 
chlorine,  and  a  little  greater  than  that  of  carbonic  acid,  which 
is  1.525  ;  this  confirms  the  density  1.658. 

An  important  property  of  ozone  is  its  reduction  by  hydrogen 
dioxide,  and  the  simultaneous  decomposition  of  the  latter  com- 
pound. The  products  are  ordinary  oxygen  and  water. 

OO2     4-     H202     =      2(OO)     +     H20 

Ozone.      Hydrogen  dioxide.  Ordinary  oxygen.          Water. 


THE    ATMOSPHERE. 


63 


ATMOSPHERIC   AIR. 

The  air  is  a  mixture  of  oxygen  and  nitrogen.  It  also  con- 
tains traces  of  carbonic  acid  gas  and  a  variable  proportion  of 
vapor  of  water. 

Its  composition  was  established  by  Lavoisier  by  an  experi- 
ment that  has  become  celebrated.  Having  heated  mercury  in 
a  limited  quantity  of  air  to  a  temperature  near  its  boiling-point 
for  several  days,  he  observed  the  formation  of  a  red  powder,  a 
combination  of  the  mercury  with  oxygen.  On  the  termination 
of  the  experiment,  he  found  that  the  volume  of  the  air  had 
diminished  about  one-sixth.  He  carefully  collected  the  oxide 
formed,  introduced  it  into  a  small  retort,  and  heated  it  to  red- 
ness. He  thus  obtained  a  gas  "  eminently  qualified  to  support 
combustion  and  respiration,"  and  the  volume  of  which  was 
sensibly  equal  to  that  of  the  gas  that  had  disappeared.  This 
gas  he  named  oxygen.  He  mixed  it  with  the  irrespirable  resi- 
due from  the  first  experiment,  which  would  not  support  com- 
bustion, and  so  reconstituted  atmospheric  air.  The  composition 
of  the  latter  was  thus  established  by  analysis  and  synthesis. 
This  experiment  was  infinitely  more  instructive  than  that 
undertaken  by  Scheele  at  about  the  same  time.  The  great 
Swedish  chemist  only  absorbed  the  oxygen  of  the  air  by  the 
alkaline  sulphides.  The  nitro- 
gen remained  as  residue,  but 
the  oxygen  combined  with  the 
sulphide  could  not  be  again 
separated. 

However,  neither  one  nor 
the  other  of  these  methods 
could  give  the  exact  propor- 
tion according  to  which  the 
oxygen  and  nitrogen  are  mixed 
in  the  atmosphere.  This  has 
been  deduced  from  the  follow-  J?IQ.  22. 

ing  experiments. 

Experiments. — 1.  Into  a  small  bent  tube  closed  at  the 
upper  end,  filled  with  mercury  and  inverted  in  a  vessel  of  the 
same  metal,  are  passed  100  volumes  of  air  (Fig.  22).  A 
small  piece  of  phosphorus  is  then  introduced  and  brought 
into  the  upper  limb,  where  it  is  heated  by  the  aid  of  a  spirit- 
lamp.  It  takes  fire,  and  in  burning  consumes  all  of  the 


64  ELEMENTS    OF    MODERN    CHEMISTRY. 

oxygen  of  the  100  volumes  of  air.  The  operation  has  termi- 
nated when  the  flame  of  the  phosphorus  vapor  has  extended 
down  to  the  column  of  mercury.  The  residual  gas  is  then 

allowed  to  cool,  and  on  being  measured  is  found  to  be 

reduced  to  79  volumes.     It  is  nitrogen. 

2.  The  absorption  of  oxygen  by  phosphorus  will  take 
place  in  the  cold,  if  a  long  stick  of  this  substance  be  in- 
troduced into  a  determined  volume  of  air  contained  in  a 
graduated  tube.     The  experiment  requires  several  hours, 
and  gives  the  same  result  as  the  preceding. 

3.  100  volumes  of  air  are  measured  into  a  graduated 
tube  on  the  mercury-trough.     A  concentrated  solution 
of  potassium  hydrate  is  introduced,  and  then  some  pyro- 
gallic  acid,  a  white,  crystalline  substance  employed  in 
photography;    the  whole  is  then  rapidly  agitated,  the 
extremity  of  the  tube  being  closed  by  the  thumb. 

The  alkaline  solution  is  immediately  blackened  by  the 
destruction  of  the  pyrogallic  acid.  All  of  the  oxygen  is 
rapidly  absorbed,  and  when  the  tube  is  opened,  under 
the  surface  of  the  mercury,  the  100  volumes  of  air  are 
found  reduced  to  about  79  volumes. 


FIG.  23.  FIG.  24. 

4.  There  is  another  method  capable  of  still  greater  precision : 
Fig.  23  represents  a  Bunsen's  eudiometer ;  it  is  a  stout  glass 
tube  about  60  centimetres  long  and  2  centimetres  in  diameter. 
Two  platinum  wires  are  hermetically  sealed  into  the  upper  ex- 
tremity through  the  whole  thickness  of  the  glass.  Each  ter- 


THE    ATMOSPHERE.  65 

minates  exteriorly  in  a  small  loop,  and  on  the  interior  follows 
the  curve  of  the  end  nearly  to  the  centre,  so  as  to  leave  an 
interval  of  about  1  centimetre  between  the  extremities  of  the 
two  wires.  The  tube  is  graduated  in  millimetres,  and  the  ca- 
pacity of  each  division  is  known.  It  is  filled  with  mercury  and 
inverted  upon  a  small  trough.  100  volumes  of  air  and  100 
volumes  of  hydrogen  are  then  introduced.  One  of  the  plati- 
num loops  is  then  put  into  communication  with  an  electrical 
conductor,  and  the  other  with  the  earth,  and  a  spark  is  passed 
through  the  mixture  (Fig.  24).  A  flash  appears  in  the  tube, 
and  all  of  the  oxygen  of  the  100  volumes  of  air  has  combined 
with  hydrogen  to  form  water.  There  thus  results  a  vacuum, 
which  is  filled  by  the  mercury,  and  in  place  of  200  volumes  of 
gas  introduced  into  the  eudiometer,  we  find,  all  corrections  being 
made,  only  137.21  volumes  of  a  mixture  of  hydrogen  and 
nitrogen. 

62.79  volumes  have  then  disappeared  to  form  water,  and 
this  water  contains  all  of  the  oxygen  contained  in  100  volumes 
of  air ;  as  each  volume  of  this  oxygen  must  consume  2  vol- 
umes of  hydrogen,  it  follows  that  the  62.79  volumes  which 
have  disappeared  must  have  contained  20.93  volumes  of 
oxygen  and  41.86  volumes  of  hydrogen. 

Hence  the  100  volumes  of  air  introduced  into  the  eudiom- 
eter contained  20.93  volumes  of  oxygen  and  79.07  volumes  of 
nitrogen. 

Such  is  the  composition  of  the  air  by  volume.  As  nitrogen 
is  lighter  than  oxygen,  these  volumetric  relations  do  not  express 
the  composition  of  the  air  by  weight.  This  was  determined 
very  exactly  by  Dumas  and  Boussingault  in  the  following 
manner. 

A  globe,  A  (Fig.  25),  having  a  capacity  of  15  or  20  litres, 
and  fitted  with  a  brass  cap  and  stop-cock,  R",  by  which  it  may 
be  connected  with  an  air-pump,  is  joined  "to  a  hard  glass  tube, 
BB',  having  a  stop-cock  at  each  end,  R  and  R',  and  filled  with 
metallic  copper.  The  air  is  exhausted  from  the  globe  and  tube, 
and  the  weight  of  each  is  then  accurately  determined. 

The  tube  BB'  is  placed  in  a  combustion-furnace,  and  by  its 
extremity  B'  is  connected  with  the  tubes  K,  I,  H,  G,  F,  E,  D, 
C.  The  tube  with  bulbs  C  contains  a  solution  of  caustic  po- 
tassa ;  the  tubes  D  and  E  are  filled  with  pumice-stone  impreg- 
nated with  caustic  potassa,  and  the  tubes  F  and  G  with  frag- 
ments of  solid  caustic  potassa ;  the  bulbs  H  contain  sulphuric 

6* 


66 


ELEMENTS    OF    MODERN    CHEMISTRY. 


acid,  and  the  last  tubes,  I  and  K,  are  filled  with  fragments  of 
pumice-stone  saturated  with  sulphuric  acid.     The  potassa  serves 

to  remove  from  the  air 
the  small  quantity  of 
carbonic  acid  gas  which 
it  contains,  and  the  sul- 
phuric acid  absorbs  the 
moisture. 

The  tube  filled  with 
copper  is  now  heated  to 
redness,  its  stop-cocks 
being  open,  and  the 
stop-cock  of  the  globe  is 
gradually  opened.  Air 
immediately  enters,  but 
it  is  first  obliged  to  tra- 
verse the  series  of  tubes, 
where  it  is  deprived 
of  its  carbonic  acid 
gas  and  vapor  of  water, 
and  also  the  tube  filled 
with  incandescent  cop- 
per, which  absorbs  the 
oxygen.  It  is  then  pure 
nitrogen  which  enters 
the  globe.  The  experi- 
ment has  terminated 
when  the  tension  of  the 
gas  in  the  globe  is  equal 
to  the  exterior  pressure, 
that  is,  when  no  more 
air  enters.  The  stop- 
cock R,"  is  now  closed. 
The  tube  and  globe  are 
allowed  to  cool,  and  are 
weighed  separately. 

The  increase  in  weight 
of  the  globe  gives  the 
weight  of  the  nitrogen 
which  has  entered. 
The  increase  in  weight  of  the  tube,  which  was  first  weighed 
exhausted  of  air,  gives  the  weight  of  the  oxygen  which  has 


THE   ATMOSPHERE.  67 

combined  with  the  copper,  plus  the  weight  of  the  nitrogen 
remaining  in  the  tube  at  the  close  of  the  experiment.  The 
weight  of  this  nitrogen  is  determined  by  exhausting  the  tube 
and  weighing  a  third  time.  The  difference  between  the  second 
and  third  weighings  indicates  the  weight  of  the  nitrogen  re- 
maining in  the  tube  at  the  end  of  the  experiment,  and  this 
weight  added  to  that  of  the  nitrogen  contained  in  the  globe 
constitutes  the  total  weight  of  nitrogen  in  the  air  analyzed. 

The  weight  of  the  oxygen  is  given  by  the  difference  between 
the  third  and  first  weighings  of  the  tube. 

By  this  method  Dumas  and  Boussingault  found  that  100 
parts  of  air  contain  by  weight 

Oxygen 23.13 

Nitrogen 76.87 

These  two  gases  are  simply  mixed  in  the  air ;  they  do  not 
exist  there  in  a  state  of  combination ;  and  the  proportions  of 
the  mixture  are  universally  the  same  with  very  slight  varia- 
tions. At  the  summits  of  the  highest  mountains,  at  the  centres 
of  the  continents,  and  over  the  vast  expanse  of  the  seas,  the 
air  has  been  shown  to  be  nearly  equally  rich  in  oxygen.  From 
a  comparison  of  a  great  number  of  analyses,  Regnault  has  es- 
tablished that  as  a  rule  the  percentage  of  oxygen  only  varies 
from  20.9  to  21.0 ;  air  which  has  been  collected  on  the  open 
sea  and  close  to  the  surface  of  the  water,  has  been  found  to 
contain  a  somewhat  smaller  amount  (20.6),  a  circumstance 
which  may  be  attributed  to  the  dissolving  action  of  the  water. 

Nitrogen  and  oxygen  are  by  far  the  most  abundant  con- 
stituents of  the  atmosphere  ;  among  the  substances  which  are 
contained  in  small  proportion  must  be  mentioned  particularly 
carbonic  acid  gas  and  vapor  of  water. 

Carbonic  Acid  Gas  and  Vapor  of  Water. — If  lime-water 
be  poured  into  a  flat  dish  and  exposed  to  the  air,  in  a  few 
hours  its  surface  will  be  found  covered  with  a  white  pellicle 
formed  of  little  crystals  of  calcium  carbonate. 

This  experiment  demonstrates  the  presence  of  carbonic  acid 
gas  in  the  atmosphere.  The  watery  vapor  may  be  condensed 
by  exposing  to  the  air  a  glass  vessel  containing  a  mixture  of  ice 
and  salt.  The  sides  of  the  vessel  soon  become  covered  with  a 
layer  of  frost,  resulting  from  the  solidification  of  the  water  which 
has  been  condensed  from  the  air  by  the  cool  surface  of  the  glass. 

The  exact  quantities  of  carbonic  acid  gas  and  vapor  of  water 


ELEMENTS    OF    MODERN    CHEMISTRY. 

contained  in  the  air  may  be  determined  by  drawing  the  latter 
through  tubes  containing  sulphuric  acid  and  caustic  potassa. 
The  aspiration  is  obtained  by  means  of  a  bottle  or  a  tin  vessel, 
V  (Fig.  26),  filled  with  water.  On  opening  the  stop-cock  r, 


Fia.  26. 

the  water  runs  out,  and  air  is  drawn  in  through  the  tubes  F 
and  E,  filled  with  fragments  of  pumice-stone  wetted  with  sul- 
phuric acid,  then  through  D  and  C,  containing  pumice-stone 
impregnated  with  caustic  potassa,  and  finally  B,  which  is  like 
the  first  two.  These  tubes  increase  in  weight  from  the  absorp- 
tion of  vapor  of  water  in  the  first  two,  and  carbonic  acid  in 
the  others.  The  difference  in  weight  of  the  tubes  F  and  E 
before  and  after  the  experiment  gives  the  proportion  of  con- 
densed water  ;  the  difference  of  D,  C,  and  B  gives  the  propor- 
tion of  carbonic  acid  gas.  The  volume  of  air  is  equal  to  that 
of  the  water  which  has  run  out  of  the  aspirator. 

According  to  the  experiments  of  Theodore  de  Saussure,  the 
quantity  of  carbonic  acid  gas  contained  in  the  air  varies  from 
4  to  6  ten-thousandths.  It  is  increased  in  inhabited  places. 
It  is  greater  at  night  than  during  the  day,  a  circumstance  that 
must  be  attributed  to  the  influence  of  vegetation.  It  is  dimin- 


THE   ATMOSPHERE. 


69 


ished  after  a  rain,  and  is  found  in  its  minimum  proportion 
above  the  surface  of  large  lakes. 

The  sources  of  this  carbonic  acid  gas  are  various.  In  cer- 
tain regions  fissures  in  the  earth  disengage  large  volumes ;  vol- 
canoes emit  immense  quantities ;  certain  spring  waters  are 
supersaturated,  and  disengage  it  in  abundance  when  they  reach 
the  surface  of  the  earth.  But  the  greater  portion  is  produced 
by  the  phenomena  of  combustion  which  take  place  on  the 
earth's  surface  ;  and  among  these  phenomena  must  be  included 
respiration,  which  is  a  slow  combustion. 

Experiment. — If  by  the  aid  of  a  glass  tube,  a  (Fig.  27),  air 
from  the  lungs  be  blown  through  lime-water,  the  latter  becomes 
clouded,  by  the  formation 
of  calcium  carbonate.  The 
carbonic  acid  gas  thus 
fixed  by  the  lime  comes 
from  the  respiration,  which 
is  an  abundant  source  of 
that  gas. 

Does  carbonic  acid  gas 
accumulate  indefinitely  in 
the  atmosphere  ?  No.  Re- 
jected and  excreted  by  ani- 
mals, it  serves  for  the  res- 
piration of  plants.  The 
green  parts  of  vegetables 
possess  the  power  of  de- 
composing this  gas  under 
the  influence  of  the  sun's 
light.  The  carbon  is  fixed,  JTIG  27. 

and  serves  for  the  nu- 
trition of  the  plant ;  the  oxygen  is  rejected,  if  not  wholly,  at 
least  in  great  part.  This  truth  is  one  of  the  most  important 
achievements  of  the  science  of  the  last  century.  It  is  due  to 
the  successive  labors  of  Priestley,  Bonnet,  Ingenhouz,  Senne- 
bier,  and  Theodore  de  Saussure. 

Independently  of  carbonic  acid  gas  and  vapor  of  water,  air 
contains  other  matters  mixed  with  or. suspended  in  it  in  very 
small  quantities.  Among  these  must  be  mentioned  : 

1.  Traces  of  ammonia,  or  rather  of  ammonium  carbonate. 
These  substances  are  dissolved  by  rain-water,  and  play  an 
important  part  in  vegetation. 


70  ELEMENTS    OF    MODERN    CHEMISTRY. 

2.  A  trace  of  hydrogen  carbide  (Boussingault). 

3.  A  small  quantity  of  nitric  acid  in  the  form  of  ammonium 
nitrate.     It  is  supposed  that  nitric  acid  is  formed  in  the  air  by 
the  direct  union  of  the  nitrogen  and  oxygen  under  the  influ- 
ence of  atmospheric  electricity.      Schbnbein  asserts  that  the 
air  contains  traces  of  ammonium  nitrite : 

(NH*)N02 

4.  A  body  which  possesses  the  property  of  imparting  a  blue 
color  to  papers  saturated  with  starch   and  potassium  iodide. 
It  is  held,  and  not  without  reason,  that  this  substance  is  ozone. 
The  phenomenon  would  also  be   caused  by  the  presence  of 
traces  of  nitrous  vapors  or  chlorine  in  the  air ;  but  Andrews 
has  shown  that  air  contains  a  principle  which  decomposes  po- 
tassium iodide,  and  loses  this  property  when  it  is  brought  to  a 
high  temperature.     This  fact  can  be  explained  if  the  air  con- 
tain ozone,  which  is  destroyed  by  heat ;  it  cannot  be  explained 
if  it  contain  chlorine  or  nitrous  vapors.     Besides,  the  air  con- 
tains only  very  slight  traces  of  ozone,  which  vary  greatly ; 
often  none  is  present.     The  relative  proportion  of  ozone  pres- 
ent is  approximately  estimated  by  the  greater  or  less  intensity 
of  the  blue  color  produced  upon  ozonoscopic  paper. 

5.  Solid  particles  suspended  in  the  air  and  carried  to  a  dis- 
tance by  the  winds.    In  perfectly  calm  air  these  corpuscles  are 
deposited,  forming  a  dust  of  which  the  composition  is  very 
variable.     It  contains  various  microscopic  vegetable  and  animal 
germs  (Pasteur). 


WATER. 

Vapor  density  compared  to  air 0.623. 

Vapor  density  compared  to  hydrogen  *     .     .     .       9. 
Molecular  weight  H20        =  18.« 

Water  is  the  product  of  the  combination  of  hydrogen  and 
oxygen  ;  its  composition  was  established  by  Lavoisier  in  1785. 

1  The  density  of  vapor  of  water  compared  to  that  of  hydrogen  is  9  ;  that 
is,  if  the  weight  of  1  volume  of  hydrogen  be  represented  by  1,  the  weight 
of  1  volume  of  vapor  of  water  will  be  9 ;  in  other  words,  vapor  of  water  is 
nine  times  more  dense  than  hydrogen  under  the  same  conditions  of  tem- 
perature and  pressure. 

2  The  weight  of  the   molecule  or  the  molecular  weight  expresses   the 
weight  of  2  volumes  of  vapor,  if  the  weight  of  1  volume  of  hydrogen  be 
represented  by  1. 


WATER. 


The  combination  takes  place  exactly  in  the  ratio  of  2  volumes 
of  hydrogen  to  1  volume  of  oxygen,  as  demonstrated  by  the 
following  experiments. 

1.  Analysis  of  Water  by  Electrolysis. — Water  slightly  acid- 
ulated with  sulphuric  acid  is  introduced  into  the  vessel  C 
(Fig.  28),  through 
the  bottom  of  which 
rise  two  platinum 
wires.  These  wires 
are  hermetically 
sealed  in  the  walls 
of  the  glass,  and  the 
free  exterior  ex- 
tremities are  con- 
nected with  the 
poles  of  a  galvanic 
battery.  The  cur- 
rent passing  through 
the  acidulated  liquid 

decomposes          the  Fio  28. 

water,1  and  bubbles 

of  gas  are  formed  and  rapidly  rise  from  the  two  platinum  wires 
which  constitute  the  poles.  If  two  small  tubes  filled  with 
water  be  inverted  over  these  wires,  the  gases  may  be  collected, 
aud  it  will  be  found  that  the  gas  disengaged  at  the  negative 
pole  is  sensibly  double  in  volume  that  disengaged  at  the  posi- 
tive. The  first  is  hydrogen,  and  the  second  oxygen,  and  the 
proportion  in  which  these  gases  ape  set  free  would  be  exactly 
that  of  2  to  1,  were  it  not  that  a  small  quantity  of  oxygen  re- 
mains dissolved  in  the  acid  liquid,  or,  under  certain  condi- 
tions, combines  with  a  portion  of  the  water  surrounding  the 
negative  pole  to  form  a  trace  of  hydrogen  dioxide,  as  will  be 
mentioned  farther  on. 

This  experiment  of  the  decomposition  of  water  by  the  pile 
was  made  for  the  first  time,  in  1801,  by  two  English  physi- 
cists, Nicholson  and  Carlisle. 

1  Under  these  conditions,  it  is  really  the  sulphuric  acid  which  is  decom- 
posed; H2SO*  breaks  up  into  H2,  which  is  liberated  at  the  negative  pole, 
and  SO4,  which  separates  at  the  positive  pole,  and  is  at  once  decomposed 
into  SO3  and  0.  The  0  is  disengaged,  and  the  SO3  in  the  presence  of  the 
water  becomes  again  hydrated,  reforming  sulphuric  acid.  SO3  +  H20  == 
H2SO*.  The  electrolytic  action  is  thus  confined  to  the  sulphuric  acid, 
which  alone  is  decomposed. 


*T2  ELEMENTS    OF    MODERN    CHEMISTRY. 

2.  Eudiometric  Synthesis. — The  composition  of  water  can 
be  established  by  synthesis,  that  is,  by  the  combination  of  the 
two  elements,  hydrogen  and  oxygen.     The  experiment,  which 
is  made  in  an  eudiometer,  has  already  been  described  (page  28). 
It  demonstrates  that  the  two  gases  combine  in  the  exact  ratio 
of  2  volumes  of  the  first  to  1  of  the  second,  and  that  these 
3  volumes  of  gas  are  condensed  into  2  volumes  of  vapor  of 
water. 

These  experiments  establish  the  volumetric  composition  of 
water ;  its  composition  by  weight  can  be  deduced  from  them, 
the  densities  of  hydrogen  and  oxygen  being  known ;  for  the 
weighable  matter  of  2  volumes  of  hydrogen  being  added  to  the 
weighable  matter  of  1  volume  of  oxygen,  it  is  only  necessary 
to  add  twice  the  weight  of  1  volume  of  hydrogen  to  the  weight 
of  1  volume  of  oxygen  in  order  to  determine  the  weight  of  2 
volumes  of  vapor  of  water.  That  is  to  say,  the  ratio  by  weight 
in  which  hydrogen  combines  with  oxygen  to  form  water  is  that 
of  double  the  density  of  hydrogen  (the  weight  of  2  volumes  of 
H)  to  the  density  of  oxygen  (the  weight  of  1  volume  of  0). 
This  ratio  is 

2  X  0.0693  _  0.1386  _  1 
1.1056~   ~  1.1056  ~8 

It  may  be  deduced  in  a  more  simple  manner  by  a  com- 
parison of  the  densities  of  hydrogen  and  oxygen.  If  1  volume 
of  hydrogen  weighs  1,  1  volume  of  oxygen  weighs  16 ;  the 
weight  of  2  volumes  of  hydrogen  will  then  be  2,  and  it  will  be 
seen  that  the  two  gases  unite,  by  weight,  in  the  ratio  of 

1—1 

16~8 

18  grammes  of  water  then  contain  16  grammes  of  oxygen 
and  2  grammes  of  hydrogen.  This  composition,  which  can  be 
determined  only  in  an  approximative  manner  by  a  compari- 
son of  the  densities,  owing  to  the  difficulties  in  the  methods 
of  weighing  gases,  has  been  established  in  the  most  rigorous 
manner  by  Dumas,  in  an  experiment  which  has  become  classic, 
and  will  now  be  described. 

3.  Synthesis  of  Water  by  the  Gravimetric  Method. — In  order 
to  determine  the  composition  of  water  by  synthesis  it  is  suffi- 
cient to  combine  an  indeterminate  quantity  of  hydrogen  with 
a  precisely  determined  weight  of  oxygen,  and  to  weigh  exactly 
the  water  formed.    By  subtracting  from  this  latter  weight  that 


WATER. 


of  the  oxygen  contained  in  the  water,  the  weight  of  the  hydro- 
gen which  has  com- 
bined with  that  oxy- 
gen is  obtained. 

In  order  to  thus 
combine  hydrogen 
with  oxygen,  it  is 
convenient  to  make 
the  former  gas  react 
upon  an  oxidized 
body  which  will  read- 
ily yield  its  oxygen 
to  the  combustible 
gas.  Cupric  oxide,  or 
black  oxide  of  cop- 
per, CuO,  first  sug- 
gested by  Gray-Lus- 
sac,  and  employed  for 
this  purpose  by  Ber- 
zelius  and  Dulong, 
fulfils  these  condi- 
tions. Although  un- 
decomposable  by  heat 
alone,  it  is  readily  re- 
duced by  hydrogen 
when  heated  in  an  at- 
mosphere of  that  gas. 
Dumas  employed  the 
apparatus  represent- 
ed in  Fig.  29. 

Hydrogen  is  pre- 
pared by  the  action 
of  dilute  sulphuric 
acid  upon  zinc,  and 
is  purified  by  being 
conducted  through  a 
series  of  U  tubes,  the 
first  containing  frag- 
ments of  glass  wet 
with  a  solution  of  lead 
acetate,  the  second, 
fragments  of  glass  wet  with  a  solution  of  silver  sulphate,  and 


74  ELEMENTS    OF    MODERN    CHEMISTRY. 

the  third,  pumice-stone,  impregnated  with  caustic  potassa. 
The  lead  acetate  retains  hydrogen  sulphide  ;  the  silver  sulphate 
absorbs  hydrogen  arsenide,  and  the  potassa  absorbs  any  traces 
of  carbides  of  hydrogen. 

The  hydrogen  thus  purified  is  dried  by  passage  through  an- 
other series  of  U  tubes,  the  first  containing  calcium  chloride, 
and  the  others  pumice-stone  saturated  with  sulphuric  acid.  The 
latter  tubes  are  cooled  by  being  surrounded  with  ice.  The  gas 
is  lastly  passed  through  a  smaller  tube  containing  phosphoric 
oxide.  The  weight  of  this  tube  must  remain  constant  during 
the  whole  of  the  experiment.  It  is  called  the  witness-tube. 

The  pure  and  dry  hydrogen  now  passes  through  a  green 
glass  bulb,  which  contains  pure  cupric  oxide.  The  weight  of 
this  bulb,  together  with  the  oxide  which  it  contains,  is  deter- 
mined with  care.  The  receiver  B',  as  well  as  the  U  tubes 
which  terminate  the  apparatus,  are  also  accurately  weighed. 

When  the  whole  of  the  air  contained  in  the  apparatus  has 
been  expelled  by  the  hydrogen,  the  flask  is  heated  and  the 
cupric  oxide  is  reduced.  Water  is  formed  and  is  in  great  part 
condensed  in  the  liquid  state  in  the  receiver,  but  a  portion  of 
the  vapor  remains  uncondensed  and  is  carried  off  by  the  excess 
of  hydrogen.  This  vapor  is  retained  in  the  second  series  of 
U  tubes,  which  contain  calcium  chloride  and  pumice-stone  satu- 
rated with  sulphuric  acid.  When  the  reduction  has  almost 
terminated,  the  bulb  is  allowed  to  cool,  the  current  of  hydro- 
gen being  continued  ;  this  gas  is  finally  displaced  by  a  current 
of  air,  and  the  weighings  are  then  made. 

The  weight  of  the  bulb  has  decreased  by  that  of  all  of  the 
oxygen  which  has  been  taken  from  the  oxide  of  copper  by  the 
hydrogen,  and  which  now  exists  in  the  water  formed. 

The  weight  of  the  receiver  and  the  condensing  apparatus  con- 
nected with  it  is  increased  by  the  weight  of  all  the  water  formed. 

By  subtracting  the  weight  of  the  oxygen  from  that  of  the 
water  we  find  the  weight  of  the  hydrogen. 

By  the  aid  of  this  rigorous  method  Dumas  has  found  that 
100  parts  by  weight  of  water  contain 

Hydrogen 11.11 

Oxygen 88.89 

100.00 

These  numbers  are  in  the  exact  ratio  of 

Hydrogen 1 

Oxygen  .     .     . 8 


WATER.  75 

Physical  Properties. — Pure  water  has  neither  taste  nor 
odor.  It  is  limpid  and  colorless.  It  occurs  in  three  states  in 
nature  ;  during  the  colds  of  winter  it  is  solid.  Ice,  snow,  frost, 
sleet,  and  hail  are  the  different  forms  which  it  assumes  in  this 
state.  The  temperature  at  which  ice  melts  is  one  of  the  stand- 
ard points  in  the  thermometric  scale.  To  this  temperature 
corresponds  the  0  of  the  centigrade  scale,  which  is  adopted  in 
this  work. 

Snow  is  composed  of  an  agglomeration  of  little  crystals; 
these  are  hexagonal  prisms,  which  often  present  the  forms  rep- 
resented in  Fig.  30. 


FIG.  30. 

At  the  moment  of  freezing,  water  expands,  and  its  density 
is  then  less  than  that  which  it  possesses  in  the  liquid  state. 
The  density  of  ice  is  0.93.  Water  contracts  in  volume  from 
0  to  -f  4°,  and  presents  its  maximum  density  at  the  latter  tem- 
perature. Its  density  at  this  point  is  chosen  as  the  unit  of 
comparison  for  the  densities  of  solid  and  liquid  bodies. 

Water  and  even  ice  are  continually  emitting  invisible  vapors 
which  mix  with  the  air,  and  are,  as  it  were,  dissolved  in  it. 
This  vaporization  takes  place  more  actively  as  the  temperature 
is  raised. 

The  air  is  said  to  be  saturated  with  vapor  at  any  given  tem- 
perature when  it  refuses  to  take  up  any  more  vapor  at  that 
temperature.  Under  these  conditions,  if  the  temperature  be 
lowered,  a  portion  of  the  vapor  is  condensed  in  fine  drops, 
which  remain  suspended  in  the  air  in  the  form  of  mist  or  visi- 
ble vapor.  The  point  at  which  the  moisture  of  the  air  is  con- 
densed is  called  the  dew-point. 

Water  begins  to  boil  when  its  vapor  acquires  sufficient  ten- 
sion to  overcome  the  atmospheric  pressure.  This  is  the  boil- 
ing-point, and  under  a  pressure  of  0.760  metre  corresponds  to 
100°  of  the  centigrade  scale. 


76 


ELEMENTS    OF    MODERN    CHEMISTRY. 


Chemical  Properties. — Water  is  partially  decomposed  by 
the  highest  temperatures  at  our  command.  On  pouring  melted 
platinum  into  an  iron  mortar  containing  water,  Grove  observed 
a  disengagement  of  bubbles  composed  of  an  explosive  mixture 
of  oxygen  and  hydrogen.  According  to  H.  Sainte-Claire  De- 
ville,  vapor  of  water  undergoes  a  partial  decomposition,  which 
he  calls  dissociation,  when  exposed  to  a  temperature  between 
1100  and  1200°.  In  order  to  collect  the  gases  resulting  from 
this  decomposition  it  is  necessary  to  separate  them  before  they 
have  reached  a  part  of  the  apparatus  where  a  less  elevated 
temperature  would  permit  their  recombination.  For  this  pur- 
pose Deville  directed  a  current  of  steam  through  a  porous  clay 
tube,  a  (Fig.  31),  surrounded  by  a  tube  of  glazed  porcelain,  b, 


FIG.  31. 

which  was  heated  to  whiteness  in  a  powerful  furnace.  A  cur- 
rent of  carbonic  acid  gas  was  passed  through  the  annular  space 
between  the  two  tubes,  by  means  of  the  tube  c.  The  vapor  of 
water  was  decomposed  by  the  heat  into  hydrogen  and  oxygen  ; 
but  these  two  gases  separated  from  each  other :  the  hydrogen, 
being  the  more  diffusible,  passed  in  great  part  through  the 
porous  tube,  while  the  oxygen  was  delivered  by  the  interior 
tube,  together  with  a  small  quantity  of  carbonic  acid  gas,  which 
entered  by  diffusion.  The  gases  evolved  by  the  two  tubes  were 
collected  in  a  small  jar  filled  with  a  solution  of  caustic  potassa 
by  which  the  carbonic  acid  gas  was  absorbed,  and  there  re- 
mained an  explosive  mixture  of  hydrogen  and  oxygen. 

Water  is  decomposed  by  an  electric  current,  as  already  seen. 


WATER.  77 

It  is  likewise  decomposed  by  many  of  the  elements,  metallic 
and  non-metallic,  which  combine  with  one  or  the  other  of  its 
component  elements.  Thus,  chlorine  decomposes  it  at  a  red 
heat,  uniting  with  the  hydrogen  to  form  hydrochloric  acid,  and 
setting  free  the  oxygen ;  also  under  the  influence  of  light  at 
ordinary  temperatures.  A  number  of  the  metals  decompose 
water,  liberating  the  hydrogen. 

Iron  decomposes  it  at  a  red  heat,  taking  up  the  oxygen  and 
setting  free  the  hydrogen ;  potassium  and  sodium,  as  we  have 
seen  in  the  case  of  the  latter  metal,  produce  the  same  effect  at 
ordinary  temperatures. 

Many  compound  bodies  seize  upon  the  elements  of  water, 
and  are  decomposed  by  it.  Such  are  the  chlorides  of  phos- 
phorus and  antimony.  In  these  reactions,  which  will  be 
studied  farther  on,  the  hydrogen  of  the  decomposed  water 
unites  with  the  chlorine,  the  oxygen  with  the  other  element. 

We  have  already  noticed  the  action  of  water  upon  the  non- 
metallic  and  metallic  oxides.  It  combines  with  many  of  these 
compounds,  forming  either  acids  or  metallic  hydrates. 

Certain  of  these  reactions  are  worthy  of  reconsideration.  It 
is  especially  important  to  fully  appreciate  the  part  played  by 
the  water  which  enters  into  them. 

When  potassium  oxide  becomes  hydrated  to  form  caustic 
potassa,  the  reaction  takes  place  by  a  double  decomposition, 
which  may  be  expressed  by  the  following  equation  : 

a)l}°  +  1}°  = 

Potassium  oxide.  Water.  Potassium  hydrate.    Potassium  hydrate. 

It  will  be  seen  that  both  the  potassium  oxide  and  the  water 
are  converted  into  potassium  hydrate  by  the  exchange  of  an 
atom  of  potassium  for  an  atom  of  hydrogen.  Potassium  hydrate 
is,  as  it  were,  derived  from  water  by  the  substitution  of  an  atom 
of  potassium  for  an  atom  of  hydrogen.  This  substitution  takes 
place  directly  when  water  is  decomposed  by  potassium. 

(2)  2H20  -f  K2  =  2KOH  +  H2 

The  potassium  hydrate  in  its  turn  may  lose  the  remaining 
atom  of  hydrogen  ;  if  it  be  heated  with  potassium,  this  hydro- 
gen is  displaced,  and  potassium  oxide  is  formed. 

(3)  2KOH      +      K2      =      2K2O      +      H2 

Potassium  hydrate.        Potassium.        Potassium  oxide.         Hydrogen. 


78  ELEMENTS    OF    MODERN    CHEMISTRY. 

It  will  be  seen  from  what  precedes  that,  starting  with  water, 
we  may  form  potassium  hydrate  (2),  potassium  oxide  (3),  and 
this  again  may  be  converted  into  potassium  hydrate  (1).  The 
three  compounds  are  then  closely  related.  Each  contains  1 
atom  of  oxygen  combined  with  2  atoms  of  another  body,  hy- 
drogen or  potassium,  and  the  relation  is  clearly  expressed  in 


the  following  formulae  : 


1}° 


Water.  Potassium  hydrate.    Potassium  oxide. 

If  hypochlorous  oxide,  CPO,  be  poured  into  water,  it  is  in- 
stantly dissolved  and  converted  into  hypochlorous  acid.  The 
reaction  is  expressed  in  the  following  equation  : 

cnn          H|O         H  )0         ciin 

Cl  }  C      +      H  I  C  Cl  I  C     +      H  J  |  C 

Hypochlorous  oxide.  Water.  Hypochlorous  acid.     Hypochlorous  acid. 

Both  the  hypochlorous  oxide  and  the  water  are  converted 
into  hypochlorous  acid  by  the  exchange  of  an  atom  of  hydro- 
gen for  an  atom  of  chlorine,  so  that  the  hypochlorous  acid 
may  be  said  to  represent  water  in  which  1  atom  of  chlorine  is 
substituted  for  an  atom  of  hydrogen. 

Thus,  by  their  atomic  constitution  both  potassium  hydrate 
and  hypochlorous  acid  are  closely  related  to  water.  But  on 
comparing  them  together  they  are  found  to  differ  widely  in 
their  properties,  both  from  each  other  and  from  water  itself. 
How  could  it  be  otherwise  with  bodies  containing  elements  as 
unlike  as  potassium  and  chlorine  ?  Indeed,  the  distance  which 
separates  potassium  hydrate  and  hypochlorous  acid  is  not 
greater  than  that  which  separates  potassium  and  chlorine. 
Thus,  a  difference  of  elements  may  imply  a  marked  difference  of 
properties  between  bodies  which  otherwise  present  a  similar  con- 
stitution, and  which  may  be  said  to  belong  to  the  same  type. 

Water  is  one  of  these  types.  Its  constitution  serves  as  a 
sort  of  model  for  that  of  a  multitude  of  compounds.  It  will  be 
sufficient  to  reconsider  the  examples  already  cited,  and  we  may 
say  that  water,  potassium  hydrate,  potassium  oxide,  hypochlo- 
rous acid,  and  hypochlorous  oxide  belong  to  the  water  type. 


. 

)0         Cl)0         HJ0 
p          H  P          HP 


Cl 

Ci 

Hypochloroua      Hypochlorous  Water.  Potassium  Potassium 

oxide.  acid.  hydrate.  oxide. 


WATER.  79 

The  preceding  considerations  give  but  a  limited  idea,  but 
one  sufficient  for  the  present,  of  the  role  played  by  water  in 
chemical  phenomena.  This  role  is  one  of  great  importance, 
for  water  takes  part  in  an  immense  number  of  reactions,  either 
by  its  decomposition,  its  formation,  or  its  combination. 

Water  presents  still  another  mode  of  action.  It  dissolves 
very  many  bodies,  and  this  solvent  action  is  exerted  upon 
gases,  liquids,  and  solids. 

Solvent  Properties  of  Water. — When  a  gas  dissolves  in 
water,  it  changes  its  state,  it  becomes  itself  liquid,  and  in  lique- 
fying it  evolves  heat.  In  the  same  manner  a  solid  body  be- 
comes liquid  by  the  act  of  solution,  but  in  order  to  become 
liquid  it  must  absorb  heat.  Consequently,  the  solution  of  a 
gas  in  water  takes  place  with  a  production  of  heat ;  that  of  a 
solid  body  takes  place  with  a  lowering  of  temperature,  or,  to 
use  a  common  expression,  a  production  of  cold. 

But  sometimes  this  physical  phenomenon  of  the  solution  of 
a  solid  body  in  water,  that  is,  its  liquefaction  and  diffusion  in 
the  liquid,  is  complicated  by  a  chemical  action. 

Experiment. — If  water  be  poured  upon  fused  and  powdered 
calcium  chloride,  the  salt  is  instantly  dissolved  with  a  produc- 
tion of  heat.  This  heat  is  the  evidence  of  a  chemical  com- 
bination, and  the  water  has  indeed  combined  with  the  calcium 
chloride ;  if  now  the  solution  be  sufficiently  evaporated,  it  will 
deposit  fine  transparent  crystals  of  hydrated  calcium  chloride. 
The  water  contained  in  these  crystals,  and  which  is  necessary 
for  their  formation,  is  what  is  called  water  of  crystallization. 
It  is  contained  in  definite  proportions,  and  is  retained  in  the 
crystals  by  affinity.  For  this  reason  the  combination  of  water 
with  calcium  chloride  is  accompanied  by  a  production  of  heat. 

If  these  crystals  of  calcium  chloride  be  dissolved  in  water, 
they  disappear,  and  the  temperature  of  the  liquid  is  depressed. 
The  physical  phenomenon  of  the  solution  of  a  solid  body  in 
water  can  thus  be  separated  from  the  chemical  phenomenon 
of  its  combination  with  that  liquid. 

Natural  State  of  Water. — Water  is  not  met  with  in  a  pure 
state  in  nature.  Whether  it  has  rested  upon  or  has  flowed  over 
the  surface  of  the  soil,  whether  it  has  fallen  in  the  form  of  rain, 
mist,  or  dew,  or  whether  it  has  just  issued  from  its  subterranean 
passages,  it  always  contains  various  matters  in  solution. 

It  takes  up  the  gases  from  the  atmosphere,  and  also  certain 
bodies  which  it  there  finds  suspended  or  in  vapor.  On  the 


80  ELEMENTS   OF   MODERN   CHEMISTRY. 

surface  or  in  the  bosom  of  the  earth  it  dissolves  the  soluble 
substances  which  it  encounters.  Hence  the  composition  of 
natural  water  presents  great  variations,  according  to  the  origin 
of  the  water  and  the  localities  where  it  has  collected,  or  the 
soils  through  which  it  has  travelled.  In  general,  meteoric 
waters,  that  is,  those  which  result  from  the  condensation  of 
the  aqueous  vapor  diffused  through  the  atmosphere,  are  more 
pure  than  those  which  have  collected  upon  the  earth's  surface. 
The  latter  present  in  their  physical  and  chemical  properties,  in 
their  composition,  and  in  their  action  upon  the  animal  econ- 
omy, such  differences  that  they  are  classified  in  several  groups. 

Soft  or  potable  waters  are  distinguished  from  hard  waters. 
The  first  are  such  as  hold  only  small  quantities  of  foreign  mat- 
ters in  solution,  and  are  essentially  fit  for  domestic  use.  The 
second  are  too  highly  charged  with  saline  matters,  and  princi- 
pally the  salts  of  calcium,  to  be  fit  for  such  purposes.  Good 
potable  water  should  be  cool,  limpid,  without  odor,  should  have 
a  faint  but  agreeable  taste,  which  should  be  neither  insipid, 
saline,  nor  sweet,  and  should  cook  and  soften  vegetables  and 
dissolve  soap.  The  purest  water  is  not  necessarily  the  best. 
Thus  distilled  water,  rain-water,  and  that  coming  from  the 
melting  of  ice  and  snow,  although  more  pure,  are  less  salubrious 
than  good  spring  or  river  water. 

Good  potable  water  should  be  aerated,  that  is,  it  should  hold 
in  solution  the  gases  contained  in  the  atmosphere :  oxygen, 
nitrogen,  and  carbonic  acid.  Rain-water  takes  from  the  atmos- 
phere a  proportion  of  oxygen,  and  especially  of  carbonic  acid 
gas,  much  greater  than  that  in  which  these  gases  are  contained 
in  the  air.  This  must  be  so,  for  Dalton  has  shown  that  the 
solvent  action  of  water  upon  a  gaseous  mixture  is  measured  for 
each  gas  by  the  product  of  its  coefficient  of  solubility  and  the 
figure  expressing  the  proportion  of  that  gas  in  the  mixture. 
These  gases  are  driven  out  of  water  by  boiling. 

The  following  figures  give  the  proportions  of  the  atmospheric 
gases  expelled  by  boiling  from  a  litre  of  water  from  the  Seine, 
in  the  month  of  January,  and  also  the  proportions  contained  in 
a  litre  of  rain-water  (Peligot) : 

Water  of  the  Seine.  Rain-Water. 

Carbonic  acid  gas  .     .     22.6  cubic  centimetres.     0.5  c.  c.  1.77 

Nitrogen 21.4                                   15.1  64.47 

Oxygen 10.1                                     7.4  33.76 

54.1                                    23.0  100.00 


WATER.  81 

It  is  seen  that  the  running  water  contains  a  larger  amount 
of  all  of  the  gases  than  rain-water,  and  a  notably  larger  pro- 
portion of  carbonic  acid. 

Solid  Matters  dissolved  in  Water. — Soft  waters  generally 
contain  a  small  proportion  of  fixed  matters,  among  which  are 
certain  salts  of  calcium  and  magnesium,  certain  alkaline  salts, 
silica,  and  organic  matters. 

The  calcium  salts  are  the  carbonate  and  sulphate,  and  some- 
times traces  of  the  chloride,  nitrate,  and  phosphate. 

Calcium  carbonate,  or  carbonate  of  lime,  is  almost  insoluble 
in  pure  water,  but  dissolves  readily  in  water  charged  with 
carbonic  acid  gas ;  in  such  solutions  it  exists  as  dicarbonate. 
When  water  thus  charged  with  calcium  dicarbonate  is  boiled, 
that  salt  is  decomposed,  carbonic  acid  gas  is  disengaged,  and 
neutral  calcium  carbonate  is  precipitated.  'When  the  propor- 
tion of  calcium  dicarbonate  contained  in  spring-water  is  large, 
it  may  happen  that  as  the  water  loses  carbonic  acid  gas  the 
calcium  carbonate  is  deposited  at  ordinary,  temperatures.  This 
effect  is  favored  by  the  tumultuous  movements  to  which  spring- 
water  is  subjected  either  in  flowing  over  an  inclined  bed  or  in 
conducting-pipes.  The  carbonate  then  forms  a  crystalline  de- 
posit, which  incrusts  the  interior  walls  of  the  pipes  and,  in 
general,  whatever  objects  may  be  plunged  into  such  waters, 
which  for  this  reason  are  called  incrusting  or  petrifying 
waters. 

The  presence  of  small  quantities  of  calcium  dicarbonate  in 
drinking-water  may  be  considered  as  a  good  condition,  from  a 
hygienic  stand-point,  for  the  system  needs  calcareous  salts  for 
the  development  and  nutrition  of  the  bony  structures. 

Calcium  sulphate,  or  sulphate  of  lime,  exists  in  solution  in 
many  waters,  especially  in  spring  and  well  waters.  When  the 
proportion  does  not  exceed  fifteen  or  twenty  centigrammes  per 
litre,  such  water  may  be  used  without  inconvenience  for  do- 
mestic purposes.  Water  largely  charged  with  calcium  sulphate 
is  called  selenitous  water  ;  it  does  not  become  clouded  on  ebul- 
lition. Like  all  other  strongly  calcareous  water,  it  does  not  dis- 
solve soap  without  first  forming  a  flocculent  precipitate.  Salts 
of  barium  produce  with  such  water  an  abundant  white  precipi- 
tate of  barium  sulphate,  which  is  insoluble  in  nitric  acid.  Such 
water  is  unfit  for  economic  purposes. 

In  general,  the  proportion  of  calcareous  salts  in  potable  water 
should  not  exceed  five  or  six  decigrammes  per  litre ;  water 
D* 


82  ELEMENTS    OF    MODERN    CHEMISTRY. 

containing  more  than  this  is  difficult  to  digest,  and  is  called 
hard  water. 

Mineral  or  Medicinal  Waters. — These  are  waters  that  by 
virtue  of  their  temperature  or  chemical  constituents  exercise 
a  special  action  upon  the  animal  economy,  and  consequently 
have  a  therapeutic  value. 

They  are  cold  or  warm.  They  are  called  warm  when  their 
temperature  at  the  moment  of  emergence  is  above  12  or  15°. 
Of  course  their  temperatures  vary  greatly,  covering  the  whole 
thermometric  scale  from  25  to  100°.  There  are  numerous  hot 
springs  in  California,  Colorado,  and  Virginia.  The  tempera- 
ture of  the  Grand  Geyser  in  Iceland  is  even  above  100°  in  the 
depths  of  the  tube  from  which  it  issues.  According  to  their 
chemical  constituents,  mineral  waters  are  classified  in  a  number 
of  characteristic  groups,  distinguished  either  by  the  predomi- 
nance of  certain  constituents,  or  by  the  presence  of  principles 
particularly  active.  These  groups  are  as  follows : 

Acidulous  or  gaseous  waters,  characterized  by  the  presence 
of  free  carbonic  acid. 

Alkaline  waters,  characterized  by  the  presence  of  a  greater  or 
less  proportion  of  sodium  dicarbonate,  or  of  an  alkaline  silicate. 

Chalybeate  waters,  holding  a  salt  of  iron  in  solution. 

Saline  waters,  or  those  containing  certain  neutral  salts. 

Sulphur  waters,  characterized  by  the  presence  of  hydrogen 
sulphide  or  other  soluble  sulphide. 

On  arriving  at  the  surface  of  the  earth,  certain  of  these 
mineral  waters  undergo  a  change  in  chemical  constitution. 
Such  are  the  sulphur  waters  which  absorb  oxygen,  as  will  be 
noticed  presently.  Those  containing  free  carbonic  acid  lose  a 
part  of  their  gas,  and  it  often  happens  that  some  of  the  car- 
bonates held  in  solution  by  an  excess  of  carbonic  acid  become 
insoluble,  and  are  deposited  after  the  escape  of  that  excess. 
This  is  the  principal  cause  of  the  deposits  which  form  in  the 
basins  and  conducting-pipes  of  many  mineral  waters.  These 
deposits  vary  greatly  in  composition  ;  sometimes  they  are  floc- 
culent  or  pulverulent,  and  collect  in  the  form  of  mud ;  some- 
times they  form  hard  concretions  or  scales.  Calcium  and 
magnesium  carbonates,  ferric  hydrate,  alumina,  and  silica  are 
the  most  ordinary  constituents  of  such  deposits.  Besides  these, 
arsenic,  various  metallic  oxides,  and  materials  which  it  would 
be  difficult  to  detect  in  the  water  itself,  are  sometimes  concen- 
trated, as  it  were,  in  these  deposits.  Thus,  arsenic  is  detected 


WATER.  83 

much  more  readily  in  the  ochrey  deposits  around  a  ferruginous 
spring  than  in  the  water  of  the  spring  itself. 

ACIDULOUS  OR  GASEOUS  WATERS. — Free  carbonic  acid  is 
the  characteristic  and  predominant  element  of  these  waters  ;  it 
is  dissolved  in  the  depths  of  the  earth  under  a  pressure  much 
greater  than  that  of  the  atmosphere ;  hence  a  certain  portion 
of  the  gas  is  disengaged  as  soon  as  the  water  emerges  from  the 
soil,  giving  rise  to  a  greater  or  less  effervescence.  Gaseous 
waters  are  cold ;  their  taste  is  piquant  at  the  moment  of  emer- 
gence, but  often  becomes  saline  or  even  alkaline  after  the  dis- 
engagement of  the  greater  part  of  the  carbonic  acid  gas.  Nat- 
ural gaseous  waters  never  consist  of  a  solution  of  carbonic 
acid  in  pure  water ;  they  always  contain  a  small  quantity  of 
saline  matters,  principally  traces  of  sodic,  calcic,  and  magnesic 
carbonates,  and  even  traces  of  chlorides  and  sulphates.  Such 
is  the  composition  of  the  celebrated  Seltzer  water  and  of  Soultz- 
matt  water.  The  water  of  certain  of  the  Saratoga  springs 
approximates  in  composition  to  Seltzer  water. 

ALKALINE  WATERS. — These  waters  possess  an  alkaline  re- 
action, either  immediately  on  their  emergence  or  after  the  loss 
of  their  free  carbonic  acid.  This  reaction  may  be  due  to  an 
alkaline  silicate,  but  is  generally  referable  to  an  alkaline  car- 
bonate. Sodium  acid  carbonate,  NaHCO3,  commonly  called 
bicarbonate  of  soda,  exists  in  nearly  all  waters  of  this  class, 
together  with  an  excess  of  carbonic  acid.  Vichy  water  con- 
tains about  5  grammes  of  this  salt  per  litre. 

CHALYBEATE  WATERS. — Nearly  all  waters  contain  traces 
of  iron  in  solution ;  chalybeate  waters  are  such  as  contain 
sufficient  of  that  metal  to  give  them  an  astringent  taste  and 
special  therapeutic  properties.  The  iron  may  exist  in  three 
conditions : 

1.  As  ferrous  carbonate  held  in  solution  by  carbonic  acid. 

2.  As  ferrous  crenate.      Berzelius  gave  the  names  crenic 
and  apocrenic  acids  to  two  bodies  which  are  related  to  peculiar 
acids  existing  in  the  soil  or  humus,  and  which  are  known  as 
ulmic,  humic,  and  geic  acids.     Ferrous  crenate  is  soluble  in 
water ;  its  constitution  is  not  known. 

3.  As  ferrous  sulphate. 

Consequently,  chalybeate  waters  may  be  carbonated,  cre- 
nated,  and  sulphated. 

The  ferrous  salts  are  never  contained  in  these  waters  in  large 
proportions.  Many  ferruginous  waters  of  undoubted  efficacy 


84  ELEMENTS    OF    MODERN    CHEMISTRY. 

do  not  contain  more  than  4  or  5  centigrammes  per  litre. 
When  exposed  to  the  air  they  lose  the  greater  part  of  their 
carbonic  acid,  and  ferrous  carbonate  is  deposited,  but  this  loses 
its  carbonic  acid  and  is  converted  into  brown  ferric  hydrate. 
Such  is  the  manner  of  formation  and  the  nature  of  the  ochrey 
deposits  always  noticeable  around  ferruginous  springs. 

Chalybeate  waters  are  widely  diffused.  Those  of  Spa  and 
Pyrmont,  Belgium  (carbonated),  Bussang  in  the  Yosges,  and 
Forges  (crenated),  and  Passy,  at  Paris,  are  well  known.  Cele- 
brated springs  of  this  class  exist  at  Bedford,  Pennsylvania ; 
others  are  widely  diffused  throughout  the  United  States. 

SALINE  WATERS. — This  class  includes  a  great  number  of 
waters  charged  with  various  neutral  salts,  among  which  are  the 
chlorides,  bromides,  and  iodides.  The  salts  of  sodium,  mag- 
nesium, and  calcium  are  those  more  usually  met  with  in  these 
waters.  According  to  the  predominating  or  peculiarly  active 
principle  present,  they  are  classified  as  chlorinated,  sulphated, 
and  bromo-iodated  waters.  The  Saratoga  springs  yield  an 
acidulo-saline  water.  • 

Chlorinated  Saline  Waters. — The  chlorides  generally  found 
in  mineral  waters  are  those  of  sodium,  magnesium,  and  cal- 
cium ;  the  former  is  much  the  more  abundant,  and  constitutes 
one  of  the  most  common  constituents  of  mineral  waters.  It 
communicates  to  them  a  pure  salty  taste,  free  from  bitterness. 
A  great  number  of  saline  springs  serve  for  the  extraction  of 
sodium  chloride.  After  the  evaporation  of  the  water  and  the 
deposition  of  the  salt,  a  mother-liquor  remains  in  which  various 
less  abundant  salts  are  concentrated,  principally  the  alkaline 
bromides  and  iodides. 

Sea-water  is  a  chlorinated  water.  It  is  well  known  that  it 
contains  a  notable  proportion  of  sodium  chloride  (2.5  to  2.7 
per  cent.).  The  common  salt  is  accompanied  by  the  chlorides 
of  magnesium  and  potassium,  and  by  a  considerable  quantity 
of  magnesium  sulphate  (0.6  to  0.7  per  cent.). 

The  Dead  Sea  and  the  Great  Salt  Lake  of  Utah  are  the 
most  concentrated  saline  sources  known.  The  water  of  the 
latter  contains  20  per  cent,  of  sodium  chloride. 

Sulphated  Saline  Waters. — These  are  characterized  by  so- 
dium, magnesium,  or  calcium  sulphate.  The  springs  of  Carls- 
bad, in  Bohemia,  contain  a  large  proportion  of  sodium  sulphate, 
together  with  sodium  bicarbonate  and  sodium  chloride. 

The  purgative  waters  of  Epsom,  England,  contain  magne- 


HYDROGEN    DIOXIDE.  85 

slum  sulphate.  The  waters  of  Sedlitz,  Saidschiitz,  and  Pullna, 
in  Bohemia,  contain  magnesium  sulphate  and  sodium  sulphate. 
Their  taste  is  bitter.  The  Avon  Spring,  New  York,  is  of  this 
class. 

Bromo-iodated  Waters. — Many  mineral  waters  contain  small 
quantities  of  bromides  and  iodides,  independently  of  the  chlo- 
rides which  generally  exist  in  much  larger  proportions.  The 
water  of  the  Dead  Sea,  so  rich  in  magnesium  and  sodium 
chlorides,  contain  0.43  per  cent,  of  magnesium  bromide.  The 
Iodine  Spring  at  Saratoga  contains  a  notable  proportion  of 
alkaline  iodides. 

SULPHUR  WATERS. — By  this  name  are  designated  those 
waters  containing  a  soluble  sulphide  or  sulphuretted  hydro- 
gen. They  are  either  natural  sulphur  waters  or  accidental 
sulphur  waters.  The  first  contain  sodium  sulphide  ;  they  are 
generally  warm,  and  contain  but  little  solid  matter.  They  all 
disengage  nitrogen  on  their  emergence  from  the  soil.  They 
contain  a  nitrogenized  organic  matter  (baregine),  and  some- 
times deposit  a  gelatinous  precipitate  (glairine). 

Celebrated  springs  exist  in  the  Pyrenees  and  at  Bagneres- 
de-Luchon.  The  sulphur  springs  of  Sharon  and  Avon,  in  New 
York,  and  the  Red  and  White  Sulphur  Springs  of  Virginia 
are  well  known. 

Accidental  sulphur  waters  are  those  which  are  formed  upon 
the  spot  by  the  reduction  of  sulphates,  and  particularly  calcium 
sulphate,  contained  in  the  waters.  This  reduction  is  accom- 
plished by  the  action  of  organic  matters  which  impregnate  the 
soil,  and  of  which  the  combustible  elements,  carbon  and  hydro- 
gen, remove  the  oxygen  of  the  sulphates.  It  is  thus  that  the 
sulphur  water  of  Enghien  is  formed  at  the  gates  of  Paris. 

HYDROGEN  DIOXIDE. 

H2O2 

This  remarkable  compound  was  discovered  by  Thenard  in 
1818.  It  is  formed  by  the  action  of  barium  dioxide  upon  di- 
lute hydrochloric  acid.  Barium  dioxide,  powdered  and  made 
into  a  fine  paste  with  water,  is  introduced  by  small  portions 
into  cold  and  dilute  hydrochloric  acid.  It  dissolves  without 
disengagement  of  gas,  yielding  barium  chloride  and  hydrogen 
dioxide. 

BaO2       4-     2HC1      =      Bad2      +      H202 

Barium  dioxide.    Hydrochloric  acid.    Barium  chloride.    Hydrogen  dioxide. 
8 


86  ELEMENTS    OF    MODERN    CHEMISTRY. 

The  barium  chloride  is  converted  into  sulphate,  which  pre- 
cipitates, by  the  cautious  addition  of  dilute  sulphuric  acid,  and 
at  the  same  time  hydrochloric  acid  is  regenerated,  so  that  an 
additional  quantity  of  barium  dioxide  may  be  added,  and  the 
operation  is  several  times  repeated. 

Bad2     +     H2S04     =     BaSO     +     2HC1 

Sulphuric  acid.       Barium  sulphate. 

The  barium  chloride  finally  remaining  in  solution  is  exactly 
precipitated  by  a  solution  of  silver  sulphate,  and  the  hydrogen 
dioxide  poured  off  and  evaporated  in  vacuo. 

Pure  hydrogen  dioxide  is  a  syrupy,  colorless,  odorless  liquid, 
having  a  density  of  1.452.  It  is  very  unstable,  and  readily 
gives  up  half  of  its  oxygen,  being  converted  into  water.  This 
decomposition  takes  place  with  a  brisk  effervescence  when  the 
dioxide  is  heated  towards  100°  ;  it  is  also  produced  by  con- 
tact with  a  great  number  of  bodies,  some  of  which  are  them- 
selves unaltered,  some  oxidized,  and  others  even  reduced. 
Hence  hydrogen  dioxide  enters  into  three  classes  of  reactions. 

1.  If  hydrogen  dioxide,  or  more  simply,  water  charged  with 
hydrogen  dioxide,  be  poured  into  a  test-tube  containing  man- 
ganese dioxide,  the  hydrogen  dioxide  is  instantly  reduced  with 
effervescence  into  water  and  oxygen.     The  manganese  dioxide 
remains  unchanged.     Finely  divided  platinum,  gold,  silver,  and 
carbon  act  in  the  same  manner. 

2.  Hydrogen  dioxide  energetically  oxidizes  arsenic  and  sele- 
nium into  arsenic  and  selenic  acids.     It  converts  lead  sulphide 
into  sulphate. 

PbS     -f     4H202    =     PbSO    +     4H20 

Lead  sulphide.  Lead  sulphate. 

3.  Potassium  permanganate,  KMnO*,  is  a  salt  very  rich  in 
oxygen  ;  it  dissolves  in  water,  forming  a  solution  having  an 
intense  purple  color.     If  hydrogen  dioxide  be  added  to  it,  it  is 
immediately  reduced  and  decolorized.     The  oxygen  from  the 
decomposition  of  the  hydrogen  dioxide  is  in  this  case  added  to 
that  from  the  reduction  of  the  permanganate,  and  both  are  dis- 
engaged in  the  free  state. 

If  hydrogen  dioxide  be  added  to  a  solution  of  potassium  di- 
chromate,  the  latter  assumes  a  deep  blue  color,  but  this  rapidly 
disappears,  giving  place  to  a  green  tint.  At  the  same  time  an 
evolution  of  oxygen  takes  place.  In  this  case  the  reaction  is 
complex :  a  portion  of  the  hydrogen  dioxide  oxidizes  the 


HYDROGEN    DIOXIDE.  87 

chromic  acid  for  an  instant  into  blue  perchromic  acid,  but  the 
latter  is  instantly  reduced,  with  disengagement  of  oxygen,  by 
another  portion  of  the  hydrogen  dioxide,  which  at  the  same 
time  loses  half  of  its  oxygen. 

The  oxygen  gas  liberated  comes  then  at  the  same  time  from 
the  perchromic  acid  and  the  hydrogen  dioxide,  both  of  which 
are  supersaturated  with  oxygen,  and  which  mutually  reduce 
each  other.  The  perchromic  acid  formed  may  be  removed 
from  the  action  of  the  excess  of  hydrogen  dioxide  by  imme- 
diately agitating  the  liquid  with  ether :  the  latter  dissolves  the 
acid  and  assumes  a  dark-blue  color. 

These  experiments  of  reduction  are  of  great  interest,  and 
permit  of  but  one  explanation.  The  fact  of  the  reciprocal 
reduction  of  two  bodies  each  supersaturated  with  oxygen  can 
only  be  explained  by  admitting  that  the  oxygen  of  one  body 
possesses  an  affinity  for  that  of  the  other,  and  that  the  oxygen 
which  is  set  free  is  formed  by  the  union  of  two  atoms,  one  from 
the  hydrogen  dioxide,  the  other  from  the  perchromic  or  per- 
manganic acid.  These  two  atoms  unite  to  form  a  molecule  of 
oxygen  OO.  This  would  represent  oxygen  in  the  free  state, 
and  occupy  two  volumes.  It  would  be  a  true  combination,  and 
we  here  encounter  for  the  first  time  the  important  notion  that 
the  atoms  of  certain  elements  are  not  isolated  when  in  the  free 
state,  but  combined  in  pairs,  each  pair  being  held  together  by 
chemical  force.  Free  oxygen  would  then  be  oxygen  oxide,  a 
combination  of  two  atoms  of  oxygen,  both  together  forming 
a  molecule,  and  occupying  two  volumes  like  the  molecule  of 
water. 

1  molecule  of  water  ....     H-O-H  =  2  volumes. 

1  molecule  of  oxygen     .     .     .     0=0  =  2  volumes. 

While  the  molecular  structure  of  free  oxygen  or  oxygen 
oxide  corresponds  in  a  measure  to  that  of  hydrogen  oxide  or 
water,  there  exists  a  peroxide  of  oxygen  which  corresponds  in 
a  measure  to  hydrogen  peroxide  ;  it  is  ozone. 

Hydrogen  dioxide H-O-O-H 

Oxygen  dioxide  (ozone) 0\  I 

X0 


88 


ELEMENTS   OF   MODERN   CHEMISTRY. 


SULPHUR 

Vapor  density  compared  to  air 2.22 

Vapor  density  compared  to  hydrogen    ....     32. 
Atomic  weight  S =32. 

Sulphur  has  been  known  from  the  greatest  antiquity.  In 
certain  volcanic  countries  it  is  found  on  the  surface  of  the  earth 
in  the  native  state.  Sicily  and  Iceland  contain  large  deposits 
in  the  neighborhood  of  extinct  volcanoes  (solfatares).  In  order 
to  separate  it  from  the  earthy  matters  which  accompany  it,  it 
is  subjected  in  Sicily  to  distillation  in  earthen  pots  (Fig.  32). 


FIG.  32. 

These  are  arranged  in  two  rows  in  furnaces,  and  communicate 
by  lateral  tubulures  with  other  pots  which  are  placed  outside 
of  the  furnace,  and  in  which  the  sulphur  vapor  is  condensed. 

Crude  sulphur  is  thus  obtained  ;  it  is  still  mixed  with  foreign 
matters,  from  which  it  is  separated  by  a  new  distillation.  This 
operation,  which  is  called  refining,  is  conducted  in  an  apparatus 
represented  in  Fig.  33. 

A  horizontal  cast-iron  cylinder,  A,  receives  the  melted  sul- 
phur from  the  vessel  C,  which  is  heated  by  the  waste  gases 
from  the  furnace,  and  which  serves  as  a  reservoir.  The  sulphur 
vapor  enters  a  large  masonry  chamber,  B,  the  floor  of  which  is 


SULPHUR. 


89 


slightly  inclined  in  order  that  the  condensed  liquid  sulphur  may 
flow  towards  a  tap,  H,  which  can  be  opened  as  is  necessary.  A 
damper,  R,  that  can  be  regulated  by  an  articulated  wire,  per- 
mits the  closing  and  opening  of  the  mouth  of  the  cylinder. 
The  vault  of  the  chamber  is  provided  with  a  safety-valve,  K, 
which  allows  of  the  escape  of  the  expanded  air. 

At  the  commencement  of  the  operation,  when  the  walls  of 
the  chamber  are  cold,  the  sulphur  condenses  in  the  form  of  a 
fine  powder,  which  is  known  as  flowers  of  sulphur.  But  when 
the  walls  of  the  chamber  become  heated  above  the  melting- 
point  of  sulphur,  the  vapor  condenses  into  a  liquid,  and  on 
opening  the  tap  at  H,  it  is  drawn  off  into  a  vessel,  E,  from 
which  it  is  distributed  into  slightly  conical  or  cylindrical  moulds, 
where  it  solidifies.  Roll  sulphur  is  thus  obtained. 


FIG.  33. 

Physical  Properties. — Sulphur  is  a  lemon-yellow  solid.  It 
is  tasteless,  odorless,  and  brittle ;  it  is  a  non-conductor  of  heat 
and  electricity.  A  stick  of  sulphur  pressed  in  the  hand  or 
plunged  into  warm  water  produces  a  crackling  sound,  and 
finally  breaks  into  pieces ;  this  is  due  to  the  unequal  expan- 
sion from  the  circumference  to  the  centre  of  the  non-conduct- 

8* 


90  ELEMENTS   OF   MODERN   CHEMISTRY. 

ing  mass  of  sulphur,  the  crystalline  particles  of  which  are  but 
slightly  held  together  by  cohesion. 

The  density  of  sulphur  is  about  2.03.  At  111.5°  it  melts 
into  a  brownish-yellow,  transparent  liquid.  If  this  liquid  be 
allowed  to  cool  slowly  until  a  crust  forms  upon  the  surface, 
and  the  crust  be  pierced  and  the  part  still  remaining  liquid  be 
decanted,  after  removing  the  crust  the  interior  of  the  vessel  is 
found  covered  with  long,  transparent,  flexible  needles  of  a 
brownish-yellow  color.  These  crystals  are  oblique-rhombic 
prisms  having  a  density  of  1.98.  This  is  not  the  only  crystal- 
line form  assumed  by  sulphur.  If  a  solution  of  sulphur  in 
carbon  disulphide  be  allowed  to  evaporate  spontaneously, 
right-rhombic  octahedral  crystals  are  deposited  having  a  den- 
sity of  2.05.  This  form  is  also  that  of  native  crystallized 
sulphur. 

Sulphur  crystallizes,  then,  in  two  distinct  forms  belonging 
to  two  distinct  crystalline  systems.  It  is  dimorphous.  It  is  a 
curious  fact  that  the  prisms  formed  by  way  of  fusion  do  not 
long  retain  their  transparence  and  their  flexibility.  When  aban- 
doned for  some  time  to  ordinary  temperatures,  they  become 
opaque  and  brittle.  They  are  then  found  to  be  traversed 
by  a  multitude  of  planes  of  cleavage,  which  are  the  faces  of 
microscopic  octahedra  similar  to  those  obtained  by  way  of 
solution. 

•  Reciprocally,  the  transparent  octahedral  crystals  become 
opaque  when  maintained  for  some  time  at  a  temperature  of 
111°;  they  are  then  transformed  into  a  multitude  of  little 
crystals  of  prismatic  sulphur.  It  is  seen  that  the  two  crystal- 
line modifications  of  sulphur  can  be  transformed  into  each 
other.  It  is  a  curious  instance  of  dimorphism. 

Sulphur  melted  in  a  sealed  tube  will  remain  liquid  for  a 
long  time  at  temperatures  below  its  ordinary  point  of  solidifi- 
cation ;  it  is  then  said  to  be  in  a  state  of  superfusion.  When 
it  finally  solidifies,  it  crystallizes  in  voluminous  octahedra 
having  the  form  of  crystallized  native  sulphur  (Schiitzen- 
berger). 

There  are  other  and  amorphous  modifications  of  sulphur. 

Experiment. — If  sulphur  be  melted  in  a  flask,  and  the  tem- 
perature be  gradually  raised  above  its  point  of  fusion,  it  as- 
sumes a  thick  consistence  and  a  dark  color.  At  220°  it  has  a 
brown-red  color  and  is  very  thick.  If  while  in  this  state  it  be 
poured  into  cold  water,  it  is  converted  into  a  soft,  transparent, 


SULPHUR.  91 

brownish-yellow,  and  elastic  mass.  It  has  lost  all  crystalline 
appearance  ;  it  has  become  amorphous,  and  is  now  soft  sulphur. 
When  abandoned  to  itself  for  several  days,  it  hardens,  becomes 
opaque,  and  reassumes  the  properties  of  ordinary  sulphur. 
This  change  takes  place  immediately  if  the  soft  sulphur  be 
heated  to  90  or  95°  ;  is  then  accompanied  by  a  sensible  disen- 
gagement of  heat  (Regnault). 

There  are  two  modifications  of  soft  sulphur.  If  it  be  treated 
with  carbon  disulphide,  a  part  of  it  is  dissolved,  and  a  residue 
remains.  The  soluble  part  constitutes  soluble  soft  sulphur; 
the  residue  is  insoluble  soft  sulphur  (Ch.  Sainte-Claire  Deville). 
In  recently-sublimed  flowers  of  sulphur  the  sulphur  exists  in 
the  amorphous  condition. 

Sulphur  boils  at  440°  ;  its  vapor  is  red.  At  500°  it  has  a 
density  of  6.654  (Dumas).  Towards  1000°  its  density  is  only 
about  one-third  as  great.  According  to  H.  Deville  and  Troost, 
the  vapor  density  of  sulphur,  determined  at  860°  and  reduced 
by  calculation  to  0°,  is  2.22.  Compared  to  hydrogen,  this 
density  is  equal  to  32,  which  is  the  normal  density  of  sulphur 
vapor,  and  gives  its  atomic  weight.  If  1  volume  of  hydrogen 
weighs  1,  1  volume  of  sulphur  vapor  weighs  32 ;  the  latter 
figure  is  therefore  the  atomic  weight  of  sulphur. 

But  at  a  temperature  a  little  above  its  point  of  ebullition 
the  vapor  density  of  sulphur  is  6.6,  or  three  times  greater  than 
at  860°  ;  this  is  accounted  for  by  the  fact  that  the  sulphur 
does  not  assume  the  true  gaseous  state  below  a  temperature  of 
860°. 

Sulphur  is  insoluble  in  water,  but  very  slightly  soluble  in 
alcohol,  a  little  more  soluble  in  ether  and  benzine.  Its  best 
solvent  is  carbon  disulphide. 

Chemical  Properties. — Sulphur  possesses  energetic  affini- 
ties. It  combines  directly  with  a  great  number  of  the  other 
elements.  It  is  well  known  that  it  is  combustible,  burning 
with  a  blue  flame.  Its  combustion  in  air  or  oxygen  produces 
sulphurous  oxide. 

Sulphur  combines  directly  with  chlorine,  bromine,  iodine, 
phosphorus,  arsenic,  and  carbon,  and  with  very  many  of  the 
metals.  Iron  and  copper  burn  in  the  vapor  of  sulphur.  The 
sulphides  thus  formed  generally  possess  the  atomic  constitution 
of  the  corresponding  oxides.  Thus,  the  compound  of  sulphur 
and  carbon,  carbon  disulphide,  is  analogous  to  carbonic  acid 
gas.  This  analogy  is  maintained  between  a  great  number  of 


92 


ELEMENTS    OF    MODERN    CHEMISTRY. 


oxygen  and  sulphur  compounds,  as  will  be  seen  by  the  follow- 
ing examples : 


H20  water. 

H2S  hydrogen  sulphide. 

KOH  potassium  hydrate. 

KSH  potassium  sulphydrate. 

CO2  carbon  dioxide. 

CS2  carbon  disulphide. 


K20  potassium  monoxide. 
K2S  potassium  monosulphide. 
BaO  barium  monoxide. 
BaS  barium  monosulphide. 
K2C03  potassium  carbonate. 
K2CS3  potassium  sulphocarbonate. 


SULPHYDRIC  ACID,  OR  HYDROGEN  SULPHIDE. 

Density  compared  to  air 1.192 

Density  compared  to  hydrogen 17. 

Molecular  weight  H2S =34. 

This  gas,  known  also  as  sulphuretted  hydrogen,  was  discov- 
ered by  Meyer  and  Rouelle,  and  studied  by  Scheele,  in  1777, 
and  by  Berthollet. 

Preparation. — Hydrogen    sulphide   may   be   prepared  by 


FIG.  34. 


gently  heating  antimony  trisulphide  in  a  flask  with  hydrochlo- 
ric acid  (Fig.  34).     The  gas  is  first  passed  through  a  wash- 


HYDROGEN    SULPHIDE. 


93 


bottle,  B,  containing  a  little  water,  and  may  then  be  collected 
over  the  pneumatic  trough. 

The  reaction  which  takes  place  is  expressed  by  the  following 
equation : 

Sb2S3        -f        6HC1  2SbCP     +     3H2S 

Antimony  trisulphjde.        Hydrochloric  acid.        Antimony  trichloride. 

The  gas  is  generally  prepared  in  the  laboratory  by  the 
reaction  of  dilute  sulphuric  acid  with  ferrous  sulphide.  The 
operation  requires  no  heat,  and  the  reaction  is  as  follows : 

FeS        +       H2SO*      ==       FeSO       +      H2S 

Ferrous  sulphide.  Sulphuric  acid.  Ferrous  sulphate. 

As  hydrogen  sulphide  is  largely  used  in  the  laboratory,  the 
apparatus  represented  in  Fig.  35  is  convenient  for  its  ready 
production.  It  is  composed  of  two  large  bottles,  of  which  the 


FIG.  35. 

lower  apertures  are  connected  by  a  large  caoutchouc  tube.  In 
one  of  these  bottles  is  placed  a  layer  of  broken  glass  or  coke, 
which  is  not  attacked  by  sulphuric  acid ;  upon  this  is  placed 
the  ferrous  sulphide  in  fragments.  The  neck  of  this  bottle  is 
closed  by  a  cork,  through  which  passes  a  glass  tube  bearing  a 
stop-cock.  The  second  bottle  is  nearly  filled  with  dilute  sul- 
phuric acid.  The  stop-cock  of  the  first  bottle  being  opened, 
the  sulphuric  acid  enters  until  it  attains  the  same  level  in  both 
bottles,  and  as  soon  as  it  reaches  the  ferrous  sulphide  the  reac- 
tion commences  and  hydrogen  sulphide  is  disengaged.  If  the 


94  ELEMENTS    OF    MODERN    CHEMISTRY. 


stop-cock  be  closed,  the  continued  evolution  of  gas  drives  the 
liquid  back  into  the  second  bottle,  until  the  disengagement  of 
gas  ceases,  which  takes  place  as  soon  as  the  sulphuric  acid  no 
longer  touches  the  ferrous  sulphide.  The  first  bottle  then 
serves  as  a  reservoir  of  hydrogen  sulphide,  containing  the  gas 
under  a  pressure  greater  than  that  of  the  atmosphere,  and 
which  can  be  increased  by  elevating  the  second  bottle.  In 
order  to  obtain  a  current  of  the  gas,  it  is  sufficient  to  open  the 
stop-cock,  and  the  flow  can  be  regulated  at  will. 

Physical  Properties. — Hydrogen  sulphide  is  a  colorless  gas. 
It  has  a  penetrating  odor  of  putrid  eggs.  Under  a  pressure  of 
17  atmospheres,  it  condenses  to  a  transparent,  strongly  refract- 
ing liquid,  having  a  density  of  about  0.91.  At  — 85.5°  this 
liquid  solidifies  to  a  white  crystalline  mass  (Faraday).  Hydro- 
gen sulphide  is  soluble  in  water.  At  0°,  one  volume  of  water 
dissolves  4.37  volumes ;  at  10°,  3.58  volumes ;  and  at  20°, 
2.90  volumes. 

Composition. — 2  volumes  of  hydrogen  sulphide  contain  2 
volumes  of  hydrogen  and  1  volume  of  sulphur  vapor. 

If  a  given  volume  of  this  gas  be  introduced  into  a  bent  tube 
over  mercury  (Fig.  22),  and  a  morsel  of  tin  be  then  introduced 
and  heated  for  about  twenty  minutes,  the  hydrogen  sulphide  is 
decomposed  ;  the  sulphur  combines  with  the  tin,  and  the  hy- 
drogen is  set  free.  After  cooling,  the  latter  gas  occupies  a 
volume  exactly  equal  to  that  of  the  hydrogen  sulphide  at  first 
contained. 

If,  then,  from  the  vapor  density  of  hydrogen  sulphi'de  ==  17 
we  subtract  the  density  of  hydrogen =     1 

we  find  the  number 16 

which  represents  half  the  density  of  sulphur  vapor. 

It  is  hence  concluded  that  one  volume  of  hydrogen  sulphido 
contains  half  a  volume  of  sulphur  vapor  to  one  volume  of  hy- 
drogen. 

It  is  also  seen  that  hydrogen  sulphide  has  exactly  the  same 
chemical  constitution  as  vapor  of  water. 

H2O  =  2  volumes  or  one  molecule  of  vapor  of  water. 

H2S  ^=  2  volumes  or  one  molecule  of  hydrogen  sulphide. 

The  analogy  between  sulphur  and  oxygen  is  here  manifested 
in  a  striking  manner.  One  atom  of  each  of  these  elements 
requires  two  atoms  of  hydrogen.  This  is.  expressed  by  saying 
that  both  oxygen  and  sulphur  are  diatomic  elements. 


HYDROGEN    SULPHIDE.  95 

Chemical  Properties.  —  Hydrogen  sulphide  is  combustible, 
burning  with  a  bluish  flame.  The  products  of  its  complete 
combustion  are  water  and  sulphurous  oxide.  When  mixed 
with  one  and  a  half  times  its  volume  of  oxygen,  it  explodes  on 
the  application  of  a  flame  or  the  passage  of  an  electric  spark. 

H2S      -f-      O3      =      SO2      +      H20 

Two  volumes.    Three  volumes.    Two  volumes.        Two  volumes. 

When  the  supply  of  oxygen  is  insufficient,  the  combustion 
is  incomplete  and  sulphur  is  deposited. 

In  the  presence  of  water,  this  oxidation  takes  place  at  ordi- 
nary temperatures,  occasioning  a  deposit  of  sulphur.  In  the 
presence  of  moisture  and  porous  matters  it  goes  further,  sul- 
phuric acid  being  formed. 

Hydrogen  sulphide  has  a  feeble  acid  reaction  ;  it  changes 
blue  litmus  to  a  wine-red  color.  When  it  reacts  with  potassium 
hydrate,  water  and  potassium  sulphydrate  are  formed. 


H} 


S      + 

Hydrogen  sulphide.    Potassium  hydrate.    Potassium  sulphydrate. 

Chlorine,  bromine,  and  iodine  decompose  hydrogen  sulphide, 
combining  with  its  hydrogen.  When  these  bodies  are  dry,  the 
action  is  energetic,  and  the  sulphur  combines  with  the  excess 
of  the  element  employed.  If  water  be  present,  the  sulphur 
is  set  at  liberty. 

Bodies  rich  in  oxygen  readily  decompose  hydrogen  sulphide. 

Experiments.  —  1.  If  a  few  drops  of  the  strongest  nitric  acid 
be  poured  into  a  jar  filled  with  hydrogen  sulphide,  the  gas  is 
instantly  inflamed.  The  nitric  acid  gives  up  oxygen,  water  is 
formed,  sulphur  is  set  free,  and  abundant  red  fumes  appear  at 
the  same  time. 

2.  If  four  volumes  of  hydrogen  sulphide  be  mixed  with  two 
volumes  of  sulphurous  oxide  over  the  mercury-trough,  a  deposit 
of  sulphur  is  at  once  formed. 

2H2S         +         SO2    =     2H20     +     3S 

Hydrogen  sulphide.      Sulphurous  oxide.         Water.  Sulphur. 

(4  volumes.)  (2  volumes.) 

Hydrogen  sulphide  decomposes  a  great  number  of  metallic 
solutions,  forming  insoluble  sulphides,  which  are  precipitated. 

Experiments.  —  1.  If  a  solution  of  hydrogen  sulphide  be 
added  to  a  solution  of  blue  vitriol  or  cupric  sulphate,  a  brown 


96  ELEMENTS   OF   MODERN   CHEMISTRY. 

precipitate  of   cupric  sulphide  is  formed.      The  reaction   is 
expressed  by  the  following  equation  : 

CuSO     -f     IPS     =     CuS     +     H'SO* 

Cupric  sulphate.  Cupric  sulphide.    Sulphuric  acid. 

2.  By  an  analogous  reaction,  a  solution  of  plumbic  acetate, 
or  a  paper  impregnated  with  that  salt,  is  at  once  blackened  by 
the  presence  of  hydrogen  sulphide. 

Hydrogen  sulphide  acts  as  a  poison  if  inhaled  in  large 
quantities  or  for  any  length  of  time. 

HYDROGEN   PERSULPHIDE. 

This  compound,  discovered  by  Thenard,  is  analogous  to  hy- 
drogen dioxide.  It  is  prepared  by  pouring,  drop  by  drop,  a 
solution  of  calcium  disulphide  into  dilute  hydrochloric  acid. 

CaS2       +       2HC1       =       CaCP       +       H2S2 

Calcium  disnlphide.    Hydrochloric  acid.     Calcium  chloride.    Hydrogen  disulphide. 

Hydrogen  disulphide  is  formed  and  collects  at  the  bottom 
of  the  vessel  in  the  form  of  a  yellowish  oil,  having  a  disa- 
greeable, irritating  odor.  Towards  60  or  70°  it  decomposes 
rapidly  into  hydrogen  sulphide  and  sulphur. 

H2S*  =  H2S  +  S 

This  decomposition  takes  place  slowly  at  ordinary  tempera- 
tures. 

Hofmann  attributes  to  this  body  the  formula  H2S3.  He  has 
obtained  a  compound  of  this  sulphide  with  an  alkaloid,  strych- 
nine, the  analysis  of  which  has  led  him  to  conclude  that  there 
are  three  atoms  of  sulphur  in  a  molecule  of  the  persulphide  of 
hydrogen. 

OXYGEN  ACIDS   OF   SULPHUR. 

1.  Sulphur  forms  three  compounds  with  oxygen  : 

0™   (  sulphurous  anhydride  or 
Sulphurous    oxide    SO2  -          ,,        »     A 


sulphur  dioxide, 
ilphuric  anhydri 
sulphur  trioxide. 

T,       11-         -j     02/-17  (recently    discovered     by 
Persulphunc  oxide  S'O7  j      Berifhelot 


a  ,  ,      .  . ,        ar\s  (  sulphuric    anhydride    or 

Sulphuric      oxide  sulphur  trioxide. 


SULPHUROUS   OXIDE.  97 

2.  By  combining  with  a  molecule  of  water,  these  oxides  are 
converted  into  the  corresponding  acids. 

502  +  H'O  =  H2S03  sulphurous  acid. 

503  +  H20  =  H2S04  sulphuric  acid. 

3.  There  are  two  other  important  acids  of  sulphur,  hypo- 
sulphurous  and  hyposulphuric  acids.    The  former  may  be  con- 
sidered as  sulpho-sulphuric  acid,  that  is,   sulphuric  acid  in 
which  1  atom  of  oxygen  is  replaced  by  an  atom  of  sulphur. 

H2S04  sulphuric  acid. 

H2(S03)S  sulpho-sulphuric  or  hyposulphurous  acid. 
Hyposulphuric  acid  may  be  considered  as  resulting  from  the 
addition  of  sulphurous  oxide  to  sulphuric  acid. 

SO2  +  H2S04  ==  H2S206  hyposulphuric  acid. 

4.  These  are  not  the  only  known  sulphur  acids. 
Hyposulphuric  acid,  which  is  called  also  dithionic  acid,  is 

the  first  of  a  series  of  acids,  each  of  which  contains  2  atoms  of 
hydrogen  and  6  atoms  of  oxygen,  the  number  of  sulphur  atoms 
regularly  increasing.  This  series  is  called  the  thionic  series. 
The  following  is  the  nomenclature  and  composition  of  the 
acids : 

H2S206  dithionic,  hyposulphuric  acid. 

H2S306  trithionic  acid. 

H2S406  tetrathionic  acid. 

H2S506  pentathionic  acid. 

5.  Schiitzenberger  has  recently  made  known  a  new  sulphur 
acid,  which  he  has  named  hydrosulphurous  acid,  and  which  is 
formed  by  the  action  of  zinc  upon  sulphurous  acid,  as  will  be 
described  farther  on.     The  composition  of  this  acid  is  repre- 
sented by  the  formula 

H2S02. 

There  is  an  interesting  relation  between  this  acid  and  sul- 
phurous and  sulphuric  acids. 

H2S02  hydrosulphurous  acid. 

H2S03  sulphurous  acid  (not  yet  isolated). 

H2SO*  sulphuric  acid. 

SULPHUROUS   OXIDE. 

Density  compared  to  air 2.234 

Density  compared  to  hydrogen 32. 

Molecular  weight  SO2 =64. 

E  9 


98  ELEMENTS    OF    MODERN    CHEMISTRY. 

Sulphurous  oxide  or  sulphurous  acid  gas  may  be  prepared 
by  decomposing  sulphuric  acid  with  copper.  The  metal  in 
small  clippings  and  the  acid  aro  introduced  into  a  flask  fitted 


FIG.  36. 

with  a  delivery-tube  (Fig.  36) ;  heat  is  applied  and  the  gas 
collected  over  the  mercury-trough.  The  reaction  which  takes 
place  is  expressed  by  the  following  equation : 

Cu     +     2H2SO*    =    CuSO4    -f     2H20     +     SO2 

Copper.  Sulphuric  acid.        Cupric  sulphate. 

A  solution  of  sulphurous  acid  in  water  is  often  needed  in 
the  laboratory.  It  may  be  conveniently  prepared  by  reducing 
sulphuric  acid  by  charcoal ;  the  products  of  the  reaction  are 
water,  and  sulphurous  and  carbonic  acid  gases. 

2H2SO*     +     C     =     2H20     4-     2S02     -f     CO2 

Sulphuric  aciil.  Carbon  dioxide. 

The  mixed  gas  is  passed  through  a  series  of  bottles  contain- 
ing water,  which  dissolves  the  sulphurous  oxide,  but  takes  up 
only  an  insignificant  quantity  of  the  carbon  dioxide. 

Physical  Properties. — Sulphur  dioxide  is  a  colorless  gas 
having  a  pungent,  suffocating  odor.  It  is  readily  liquefied  by 
being  led  into  a  vessel  surrounded  by  a  mixture  of  ice  and  salt. 
It  condenses  at  ordinary  temperatures,  under  a  pressure  of 
about  two  atmospheres.  The  liquid  has  a  density  of  1.45  ;  it 
boils  at  — 10°,  and  produces  great  cold  by  its  evaporation  ;  on 
this  account  it  is  used  for  the  manufacture  of  ice,  and  in  other 
cases  where  intense  cold  is  required.  — 73°  may  be  obtained 


SULPHUROUS   OXIDE.  99 

by  the  evaporation  of  liquid  sulphurous  acid  aided  by  double- 
acting  pumps  (Raoul  Pictet). 

Water  at  0°  dissolves  79.9  times  its  volume  of  sulphurous 
oxide,  and  only  39.4  volumes  at  20°. 

Experiments. — 1.  If  a  small  quantity  of  mercury  contained 
in  a  porcelain  capsule  be  covered  with  a  deep  layer  of  liquid 
sulphurous  oxide,  and  the  evaporation  of  the  latter  be  favored 
by  directing  a  rapid  current  of  air  over  its  surface,  the  mercury 
is  frozen  into  a  solid  button. 

2.  When  liquid  sulphurous  acid  is  poured  into  not  too  great 
a  quantity  of  water,  a  part  of  it  is  dissolved,  but  the  excess 
absorbs  heat  from  the  mass  of  liquid,  volatilizes  suddenly,  and 
the  water  is  frozen. 

Chemical  Properties. — Sulphurous  oxide  is  not  decom- 
posed by  heat.  It  is  incombustible,  and  extinguishes  burning 
bodies. 

Its  most  striking  property  is  its  affinity  for  oxygen.  If  a 
mixture  of  two  volumes  of  sulphurous  oxide  and  one  volume 
of  oxygen  be  passed  through  a  tube  containing  slightly  heated 
spongy  platinum,  the  two  gases  combine,  forming  sulphuric 
oxide  (Kuhlmann). 

A  solution  of  sulphurous  oxide  in  water  slowly  absorbs  oxy- 
gen, and  is  converted  into  sulphuric  acid.  It  may  be  admitted 
that  the  aqueous  solution  contains  the  veritable  sulphurous  acid. 

H2S03      +       O    =     H2SO 

Sulphurous  acid.  Sulphuric  acid. 

Sulphurous  acid  reduces  a  great  number  of  oxidized  bodies. 
At  ordinary  temperatures  it  takes  the  oxygen  from  iodic  acid, 
setting  free  the  iodine ;  but  the  latter  disappears  on  the  addi- 
tion of  an  excess  of  sulphurous  acid,  sulphuric  and  hydriodic 
acids  being  formed. 

H2S03  -j-  H20  +  P  =  H2SO  -f  2HI 

It  decolorizes  the  purple  solution  of  potassium  permanganate, 
forming  manganese  sulphate  and  potassium  sulphate.  It  con- 
verts arsenic  acid  into  arsenious  acid.  It  combines  directly 
with  lead  dioxide,  forming  lead  sulphate. 

PbO2     +     SO2    =    PbSO4 

Lead  dioxide.  Lead  sulphate. 

Chlorine  will  unite  directly  with  sulphurous  oxide.  If  a 
mixture  of  equal  volumes  of  chlorine  and  sulphurous  oxide  be 


100  ELEMENTS   OF   MODERN   CHEMISTRY. 

exposed  to  sunlight,  the  two  gases  combine,  forming  a  liquid 
having  a  suffocating  odor.  It  is  sulphuryl  chloride.  Its  den- 
sity is  1.66,  and  its  boiling-point  is  77°.  It  may  be  regarded 
as  sulphur  trioxide  in  which  one  atom  of  oxygen  is  replaced 
by  two  atoms  of  chlorine. 

SO3  =  (SO2  )"0  sulphuryl  oxide  or  sulphuric  oxide. 
S02CP  =  (S02/'C12  sulphuryl  chloride. 

In  these  reactions  in  which  the  sulphurous  oxide  combines 
directly  with  either  one  atom  of  oxygen  or  two  atoms  of  chlorine, 
it  plays  the  part  of  an  element ;  it  is  a  compound  radical,  and 
this  radical  is  diatomic,  because  it  unites  with  two  atoms  of  the 
monatomic  element  chlorine,  or  with  one  atom  of  the  diatomic 
element  oxygen,  which  is  equivalent  to  two  atoms  of  chlorine. 

In  the  formulae  given,  the  diatomicity  is  expressed  by  the 
accents  ". 

Sulphurous  acid  bleaches  various  vegetable  and  animal  mat- 
ters. A  bouquet  of  violets  or  a  rose  is  bleached  in  a  few  minutes 
by  a  solution  of  sulphurous  oxide. 

Sulphurous  oxide  is  employed  in  the  arts  to  bleach  wool. 

HYDRO-SULPHUROUS  ACID. 

H2SO2 

While  sulphurous  acid  reduces  a  number  of  bodies,  it  is  in 
its  turn  reduced  by  the  action  of  zinc  upon  its  aqueous  solution. 
A  yellow  liquid  is  thus  obtained  which  energetically  bleaches 
indigo  and  litmus  solutions  (Schbnbein).  Schiitzenberger  has 
shown  that  the  liquid  gifted  with  these  properties  contains  the 
zinc  salt  of  a  new  acid,  which  he  has  named  hydrosulphurous. 
This  acid  is  formed  by  the  combination  of  hydrogen  with  sul- 
phurous oxide.  The  reaction  is  expressed  by  the  following 
equations : 

H2S03       +       Zn     =     ZnSO3     +     H2 

Sulphurous  acid.  Zinc.  Zinc  sulphite. 

SO2      +      H2  '    =      H2S02 

Sulphurous  oxide.  Hydrosulphurous  acid. 

When  this  liquid  is  treated  with  very  dilute  sulphuric  acid, 
it  gives  a  liquor  of  a  dark  orange-yellow  color,  having  ener- 
getic bleaching  powers.  It  then  contains  hydrosulphurous 
acid.  It  soon  becomes  clouded  and  deposits  sulphur.  This 


SULPHUR   TRIOXIDE,  OR   SULPHUH'C   OXIOE.  101 

acid  is  not  stable,  but  its  acid  sodium  salt  is  more  so  ;  the  latter 
has  the  composition  NaHSO2.  It  readily  absorbs  oxygen  from 
the  air,  being  converted  into  sodium  acid  sulphite. 

NaHSO2  +  O  =  NaHSO3 

This  oxidation  is  also  brought  about  by  the  presence  of  cer- 
tain metallic  salts,  such  as  those  of  copper,  mercury,  and  lead. 
In  this  case  the  metal  is  reduced  and  precipitated,  and  the 
hydrosulphite  is  decomposed,  yielding  sulphurous  oxide. 

NaHSO2  -f  CuSO4   ===  NaHSO*  -f  SO2  +  Cu 

Sodium  hydrosulphite.    Cupric  sulphate.      Sodium  acid  sulphate. 

Sodium  acid  hydrosulphite  may  be  obtained  by  the  electro- 
lysis of  a  solution  of  sodium  acid  sulphite.  In  this  case  the 
hydrogen,  which  would  otherwise  be  disengaged  at  the  negative 
pole,  accomplishes  the  reduction. 

NaHSO3  +  H2  =  NaHSO2  +  H2O 


SULPHUR  TRIOXIDE,  OR  SULPHURIC   OXIDE. 

(SULPHURIC  ANHYDRIDE.) 

Vapor  density  compared  to  hydrogen 40. 

Molecular  weight  SO3 =80. 

Sulphur  trioxide  is  formed  by  the  union  of  oxygen  with  sul- 
phurous oxide  in  the  presence  of  finely-divided  platinum. 

It  is  prepared  by  gently  heating  fuming  sulphuric  acid  in  a 
retort ;  vapors  are  given  off  which,  when  condensed  in  a  re- 
ceiver surrounded  by  a  freezing  mixture,  solidify  into  a  white 
mass,  having  a  fibrous  appearance  and  a  silky  lustre. 

Sulphur  trioxide  boils  at  a  temperature  between  30  and  35°. 
At  ordinary  temperatures  it  produces  white  fumes  in  the  air 
by  condensing  the  atmospheric  moisture.  Its  most  striking 
property  is  its  affinity  for  water ;  when  thrown  into  that  liquid, 
it  becomes  hydrated  with  such  energy  that  a  portion  of  the 
water  is  suddenly  vaporized,  and  a  hissing  noise  is  produced 
similar  to  that  heard  on  plunging  a  red-hot  iron  into  water. 

Sulphuric  acid  is  formed  by  the  reaction. 

SO3  +  H20  =  H2S04 
9* 


HJ2iV  ;  \    :        SLEMSJfT^  OF    MODERN   CHEMISTRY. 

SULPHURIC  ACID. 

Molecular  weight  H2S04 : 


This  acid,  which  has  been  known  for  centuries,  was  formerly 
obtained  by  the  distillation  of  ferrous  sulphate.  Large  quan- 
tities of  it  are  now  consumed  in  the  arts,  and  it  is  manufac- 
tured in  extensive  apparatus  known  as  leaden  chambers.  Sul- 
phurous oxide  is  conducted  into  these  chambers,  where  it 
meets  with  nitric  acid,  by  which  it  is  oxidized. 

SO2     +     2HN03    =    H2S04    +     2N02 

Nitric  acid.  Nitrogen  peroxide. 

The  products  of  the  first  reaction  are  sulphuric  acid  and 
nitrogen  peroxide  (red  vapors)  ;  but  the  latter  is  decomposed 
by  steam,  which  is  injected  into  the  chamber ;  nitric  acid  is 
regenerated  and  nitrogen  dioxide  is  formed. 

3N02     +     H20    ==    2HN03     +     NO 

Nitrogen  peroxide.  Nitrogen  dioxide. 

But  the  nitrogen  dioxide  is  not  lost ;  it  combines  with  the 
oxygen  of  the  air  contained  in  the  chamber,  and  is  reconverted 
into  nitrogen  peroxide. 

NO  -f-  0  =  NO2 

The  latter  is  again  decomposed  into  nitric  acid  and  nitrogen 
dioxide  by  the  action  of  water,  and  the  sulphurous  oxide  which 
continually  arrives  in  the  chamber  always  encounters  nitric 
acid,  by  which  it  is  converted  into  sulphuric  acid.  It  is  a 
continuous  operation,  which  theoretically  leaves  no  residue, 
and  permits  of  the  conversion  of  an  indefinite  amount  of  sul- 
phurous oxide  into  sulphuric  acid. 

It  is  really  the  oxygen  of  the  air,  continually  absorbed  and 
given  up  by  the  nitrogen  dioxide,  which  effects  the  oxidation 
of  the  sulphurous  oxide ;  the  nitric  acid  is  the  direct  agent, 
and  the  nitrogen  dioxide  is  intermediate,  for  it  is  the  vehicle 
for  the  transfer  of  the  oxygen. 

Fig.  37  represents  a  section  of  a  series  of  leaden  chambers 
for  the  manufacture  of  sulphuric  acid. 

Sulphur  is  burned  in  two  furnaces,  AA,  and  the  heat  gen- 
erated is  employed  to  boil  the  water  contained  in  the  boilers 


SULPHURIC    ACID. 


103 


104  ELEMENTS   OP    MODERN   CHEMISTRY. 

above  the  flame,  the  steam  being  distributed  to  the  chambers 
by  the  pipes  c  d.  The  sulphurous  oxide,  together  with  a 
great  excess  of  air,  passes  through  the  pipes  BB  into  a  leaden 
drum,  C.  A  thin  layer  of  sulphuric  acid  charged  with  nitrous 
products  trickles  over  the  inclined  shelves  in  the  drum.  The 
gases  pass  first  into  the  chamber  C,  then  into  D,  where  they 
meet  with  nitric  acid,  which  falls  in  thin  layers  over  a  double 
cascade,  EE,  in  such  a  manner  as  to  present  a  large  surface  for 
the  action  of  the  sulphurous  oxide.  The  sulphuric  acid  which 
is  formed  in  this  chamber  is  charged  with  nitrous  products ;  it 
is  therefore  allowed  to  flow  by  the  inclined  tube  F  into  the 
chamber  C,  where  it  encounters  an  excess  of  sulphurous  oxide, 
and  which  is  called  the  denitrifier.  The  sulphurous  oxide,  the 
excess  of  air,  and  the  nitrogen  peroxide  pass  from  D  into  the 
large  chamber  HH,  into  which  steam  is  projected  by  several 
jets.  Here  the  larger  portion  of  the  sulphuric  acid  is  pro- 
duced, and  the  reaction  is  completed  in  another  chamber.  In 
the  engraving  the  last  two  chambers  are  not  fully  represented. 
The  gases  from  the  last  chamber  enter  a  refrigerator,  in  which 
the  condensation  takes  place ;  they  are  lastly  conducted  into  a 
leaden  column,  R,  filled  with  coke  which  is  kept  saturated 
with  sulphuric  acid  by  a  thin  stream  from  the  reservoir  0. 
This  acid  completely  absorbs  the  nitrogen  dioxide,  and  descends 
by  the  tube  ba  into  the  reservoir  t,  situated  near  the  furnace. 
As  soon  as  this  reservoir  is  full,  the  stop-cock  r  is  closed,  and 
/  is  opened ;  the  pressure  of  the  steam  then  forces  the  acid 
up  into  the  reservoir  #,  which  feeds  the  first  drum.  The  gas 
which  escapes  from  the  last  column,  which  is  known  as  Gay- 
Lussac's  column,  consists  of  nitrogen  charged  with  an  insig- 
nificant quantity  of  nitrous  products. 

The  acid  which  is  drawn  from  the  chambers  is  not  suffi- 
ciently concentrated,  having  a  density  of  only  about  1.5.  It 
is  first  evaporated  in  leaden  vessels  until  it  becomes  strong 
enough  to  act  upon  the  lead,  and  the  concentration  is  then  fin- 
ished in  large  platinum  retorts.  The  excess  of  water  is  thus 
driven  out.  The  concentrated  acid  possesses  a  density  of 
1.842. 

In  many  manufactories  pyrites  is  burned  instead  of  sulphur. 
Sulphurous  oxide  is  produced,  and  a  residue  of  ferric  oxide 
remains. 

Purification  of  Sulphuric  Acid. — The  sulphuric  acid  of 
commerce  contains  impurities.  It  holds  in  solution  a  small 


SULPHURIC   ACID.  105 

quantity  of  lead  sulphate,  formed  in  the  evaporating  basins  ;  it 
is  often  charged  with  nitrous  products,  and  sometimes  with  ar- 
senic acid,  when  the  sulphurous  oxide  employed  in  its  prepa- 
ration has  been  obtained  by  the  combustion  of  arsenical  pyrites. 
It  may  be  freed  from  these  impurities  by  distillation.  The 
nitrous  products  are  first  disengaged,  and  are  found  in  the  first 
portions  of  the  distillate,  which  must  be  rejected.  Pure  sul- 
phuric acid  then  passes  ;  the  lead  sulphate  and  arsenic  acid 
remain  in  the  retort  with  the  last  portions  of  the  acid,  which 
must  not  be  distilled. 

The  operation  may  be  conducted  in  a  glass  retort  connected 
with  a  cooled  receiver.  The  retort  should  be  heated  laterally 
by  an  annular  flame  so  that  explosive  evolution  of  vapor  may 
be  avoided,  and  it  is  well  to  introduce  some  platinum  wires  with 
the  acid,  and  to  cover  the  retort  with  a  sheet-iron  hood. 

Constitution  of  Sulphuric  Acid.—  Since  oxygen  combines 
directly  with  sulphurous  oxide  to  form  sulphuric  oxide,  the 
latter  may  be  regarded  as  sulphuryl  oxide,  S020. 

Sulphuric  acid  is  the  hydrate  of  this  oxide. 

SO3  +  H20  =  H2S04 

The  following  experiment  indicates  the  relations  which  exist 
between  the  elements  composing  this  hydrate. 

If  sulphuryl  chloride  be  poured  into  water,  it  disappears, 
sulphuric  acid  and  hydrochloric  acid  being  formed. 


HOH  OH     +     2HC1 

Sulphuryl  2  molecules  Sulphuric  2  molecules 

chloride.  of  water.  acid.  hydrochloric  acid. 

Sulphuric  acid  is  .thus  formed  by  the  decomposition  of  2 
molecules  of  water,  of  which  2  atoms  of  hydrogen  have  been 
removed  by  2  atoms  of  chlorine,  and  replaced  by  the  group 
SO2.  It  may  then  be  truly  said  that  sulphuric  acid  is  derived 
from  two  molecules  of  water  by  the  substitution  of  the  diatomic 
radical  (SO2)"  for  two  monatomic  atoms  of  hydrogen. 

H.OH  ,™  „  (  OH 

H.OH  3)  {OH 

2  molecules  of  water.  Sulphuric  acid. 

If  the  composition  of  sulphuric  acid  be  compared  to  that 
of  sulphuryl  chloride,  from  which  it  may  be  formed,  it  will  be 
E* 


106  ELEMENTS   OF    MODERN    CHEMISTRY. 

seen  that  both  compounds  contain  the  same  nucleus  or  radical 
SO2,  and  that  instead  of  the  two  atoms  of  chlorine  of  the 
chloride,  the  acid  contains  two  groups  OH.  The  group  OH 
is  a  residue,  as  it  were,  which  represents  a  molecule  of  water 
minus  one  atom  of  hydrogen,  and  which  is  called  hydroxyl. 
It  is  a  monatomic  group,  and  sulphuric  acid  is  formed  by  the 
saturation  of  the  affinity  of  the  diatomic  radical  sulphuryl  by 
two  monatomic  groups  hydroxyl,  which  replace  the  two  atoms 
of  chlorine  of  sulphuryl  chloride.  Williamson  has  described 
an  intermediate  compound  in  which  the  radical  sulphuryl  is 
combined  with  one  atom  of  chlorine  and  one  OH  group. 

!         SO'{OH          SO!{OH 

Sulphuryl  chloride.    Sulphuryl  chlorohydrate.        Sulphuric  acid. 

The  sulphur  in  sulphuric  acid  is  hexatomic. 

O 
HO-S-OH 

6 

Physical  Properties. — Sulphuric  acid  is  a  colorless  oily 
liquid ;  its  density  at  12°  is  1.842  (Marignac).  Its  boiling-point 
is  325°,  and  it  solidifies  at  — 34°.  If  it  be  crystallized  several 
times  at  a  low  temperature,  and  the  part  remaining  liquid  be 
decanted  off  each  time,  the  melting-point  is  gradually  raised  to 
-[-10.5°,  where  it  remains  stationary.  According  to  Marignac, 
the  acid  which  solidifies  and  fuses  at  -f-10.50  constitutes  the 
true  monohydrated  acid,  H2S04.  At  a  temperature  about  40° 
it  emits  some  fumes,  and  between  this  point  and  290°  it  disen- 
gages a  small  quantity  of  vapor  of  sulphuric  oxide.  At  290° 
it  begins  to  boil,  but  its  boiling-point  soon  rises  to  338°,  where 
it  remains.  Such  are,  according  to  Marignac,  the  properties  of 
monohydrated  sulphuric  acid.  According  to  this  chemist,  the 
acid  purified  by  simple  distillation,  and  boiling  at  325°,  still 
contains  a  small  amount  of  water. 

Chemical  Properties. — When  exposed  to  a  red  heat,  sul- 
phuric acid  decomposes  into  sulphurous  oxide,  oxygen  and 
water. 

H2S04  =  SO2  -f  O  +  H20 

Many  bodies  having  an  affinity  for  oxygen  reduce  sulphuric 


SULPHURIC   ACID.  107 

acid  by  the  aid  of  heat.     Thus  sulphur  effects  the  reduction, 
being  at  the  same  time  oxidized  to  sulphurous  oxide. 

2H2SO  -f  S  =  3S02  +  2H2O 

We  have  already  studied  the  action  of  charcoal  and  copper 
upon  sulphuric  acid  when  boiled  with  that  liquid,  and  we  have 
seen  that  zinc  and  iron  decompose  the  dilute  acid  with  evolu- 
tion of  hydrogen  and  formation  of  a  sulphate. 

Sulphuric  acid  has  a  strong  affinity  for  water.  When  four 
parts  of  sulphuric  acid  are  quickly  mixed  with  one  part  of 
water,  the  temperature  rises  to  above  100°.  If  the  experiment 
be  made  with  large  quantities,  it  is  not  without  danger,  and  re- 
quires prudence  lest  part  of  the  acid  be  projected  from  the  vessel. 

Experiments. — If  four  parts  of  sulphuric  acid  be  quickly 
added  to  one  part  of  snow,  the  latter  is  immediately  liquefied 
and  a  notable  elevation  of  temperature  takes  place ;  for  the 
energy  of  the  combination  of  the  sulphuric  acid  with  the  water 
is  so  great  that  the  heat  produced  by  the  union  is  greater  than 
that  consumed  in  the  liquefaction  of  the  ice. 

But  if  four  parts  of  snow  be  mixed  with  one  part  of  sul- 
phuric acid,  the  result  is  the  reverse ;  there  is  a  lowering  of 
temperature. 

The  affinity  of  sulphuric  acid  for  water  is  manifested  in  a 
number  of  reactions.  In  the  following  it  is  sufficiently  power- 
ful to  cause  the  formation  of  the  water  it  requires : 

If  a  morsel  of  sugar  be  moistened  with  sulphuric  acid,  it 
becomes  blackened  and  carbonized  in  a  few  minutes.  The  sugar 
contains  no  water  already  formed,  but  independently  of  carbon 
it  contains  hydrogen  and  oxygen  in  the  proportions  necessary 
to  form  water,  so  that  the  latter  compound  is  produced  by  the 
influence  of  the  sulphuric  acid,  and  a  carbonaceous  matter 
remains. 

This  water  which  is  absorbed  by  sulphuric  acid  with  so  much 
energy,  combines  with  the  acid  in  a  manner  analogous  to  that 
in  which  water  of  crystallization  combines  with  certain  salts. 
Indeed,  if  sulphuric  acid  to  which  18.3  per  cent,  of  water  has 
been  added  be  exposed  to  a  temperature  of  0°,  large  prismatic 
crystals  are  formed,  which  remain  solid  even  at  a  temperature 
of  -f-*7°  or  -}-80.  The  composition  of  these  crystals  is  ex- 
pressed by  the  formula  H2SO*,H20.  They  constitute  a  dihy- 
drated  acid,  for  they  result  from  the  union  of  two  molecules 
of  water  with  one  molecule  of  sulphuric  oxide. 


108  ELEMENTS   OF   MODERN   CHEMISTRY. 

Sulphuric  acid  is  a  dibasic  acid  ;  that  is,  it  contains  two  atoms 
of  hydrogen  that  are  replaceable  by  an  equivalent  quantity  of 
metal.  This  substitution  takes  place  when  the  acid  is  treated 
with  a  hydrate,  such  as  potassium  hydrate,  or  with  an  oxide, 
such  as  lead  oxide. 

H2SO     -f-     2KOH      ==       K2S04     -f     2H2O 

Potassium  hydrate.      Potassium  sulphate. 

H2S04    -f     PbO    ===     PbSO4    -f     H20 

Lead  oxide.       Lead  sulphate. 

When  saturated  with  potassium  hydrate,  the  sulphuric  acid 
is  converted  into  potassium  sulphate,  and,  in  the  salt,  two  atoms 
of  potassium  replace  the  two  atoms  of  hydrogen  of  the  acid. 
In  the  case  of  the  lead  oxide,  on  the  contrary,  the  reaction, 
which  is  only  a  double  decomposition,  takes  place  so  that  a 
single  atom  of  lead  replaces  the  two  atoms  of  hydrogen.  The 
metal  lead  is  then  said  to  be  diatomic ;  that  is,  one  atom  of 
lead  is  capable  of  replacing  two  atoms  of  a  monatomic  element 
such  as  hydrogen,  and  one  atom  of  lead  is  equivalent  to  two 
atoms  of  potassium. 

Sulphuric  acid  may  be  detected  by  the  following  reactions, 
which  are  also  applicable  to  the  soluble  sulphates. 

In  solutions  containing  sulphuric  acid  or  a  sulphate,  barium 
salts  produce  a  white  pulverulent  precipitate,  which  is  insolu- 
ble in  either  cold  or  hot  nitric  acid  ;  this  precipitate  is  barium 
sulphate.  When  mixed  with  an  excess  of  charcoal  and  heated 
to  whiteness,  it  is  converted  into  barium  sulphide. 
BaSO  +  4C  =  4CO  '  BaS 

Barium  sulphate.  Carbon  monoxide.    Barium  sulphide. 

The  sulphide  of  barium  disengages  hydrogen  sulphide  when 
it  is  moistened  with  hydrochloric  acid ;  this  gas  may  be  recog- 
nized by  its  odor  and  by  its  blackening  a  paper  impregnated 
with  lead  acetate. 

FUMING  SULPHURIC   ACID. 

Fuming  sulphuric  acid,  or  Nordhausen  sulphuric  acid,  as  it 
was  formerly  called,  can  be  regarded  as  a  combination  of  sul- 
phuric acid  and  sulphuric  oxide. 

SO'<°H 

H2S04  -f  SO3  =  H2S207  =  O 

S02< 

OH 


HYPOSULPHUROTJS   ACID.  109 

It  is  a  light-brown,  oily  liquid.  At  0°  it  solidifies  into  a  leafy 
mass.  It  gives  off  white  fumes  in  the  air.  When  heated,  it 
decomposes  into  sulphuric  oxide  and  sulphuric  acid.  It  is  ob- 
tained in  the  arts  by  the  distillation  of  ferrous  sulphate  that  has 
been  previously  transformed  into  ferric  subsulphate  by  roasting. 

This  subsulphate  is  calcined  in  stoneware  retorts  ;  it  gives 
off  sulphuric  oxide  when  it  is  perfectly  dry,  but  as  it  is  difficult 
to  entirely  free  it  from  water  of  crystallization,  the  vapor  of 
sulphuric  oxide  is  mixed  with  that  of  sulphuric  acid,  and  the 
mixed  vapors  are  condensed  in  cooled  receivers.  The  residue 
of  the  distillation  is  ferric  oxide,  Fe203. 

HYPOSULPHUROUS   OR  SULPHO-SULPHURIC 
ACID. 


This  acid  is  not  known  in  the  free  state.  When  sodium 
hyposulphite  is  treated  with  dilute  sulphuric  acid,  the  hypo- 
sulphurous  acid  set  free  is  at  once  decomposed  into  sulphurous 
acid  and  sulphur. 

Na2S203     -f     H2SO*    ==     Na2SO   +   H2S03   +   S 

Sodium  hyposulphite.  Sodium  sulphate. 

Sodium  hyposulphite  is  formed  when  sulphur  is  boiled  with 
a  solution  of  sodium  sulphite. 

Na2S03     -f     S     =     Na2S(S03) 

Sodium  sulphite.  Sodium  hyposulphite. 

It  is  a  very  soluble  salt,  forming  voluminous  crystals. 
HYPOSULPHURIC   ACID. 


If  fuming  sulphuric  acid  represent  a  combination  of  sul- 
phuric acid  and  sulphuric  oxide,  hyposulphuric  acid  can  be 
regarded  as  resulting  from  the  union  of  sulphuric  acid  with 
sulphurous  oxide. 

S03.H2SO*  fuming  sulphuric  acid. 
S02.H2SO  hyposulphuric  acid. 

Preparation.  —  Hyposulphuric  acid  is  prepared  by  passing 
sulphurous  oxide  into  water  in  which  manganese  dioxide  is  sus- 
pended. 

2S02     +     MnO2       =       MnS206 

Manganese  dioxide.    Manganese  hyposulphate. 
10 


110  ELEMENTS    OF    MODERN    CHEMISTRY. 

Manganese  hyposulphate  is  thus  formed,  and  this  is  con- 
verted into  barium  hyposulphate  by  a  double  decomposition 
with  barium  sulphide.  The  liquid  is  separated  from  the  man- 
ganese sulphide  by  filtration,  and  exactly  decomposed  with 
dilute  sulphuric  acid.  Barium  sulphate  is  precipitated,  and  the 
hyposulphuric  acid  remains  in  solution.  The  liquid  is  then 
concentrated  in  vacuo. 

Properties.  —  Hyposulphuric  acid  is  a  very  acid,  syrupy 
liquid,  having  a  density  of  1.347.  It  is  not  stable  ;  when 
boiled  it  decomposes  into  sulphuric  acid  and  sulphurous  oxide. 

PERSULPHURIC   OXIDE. 


This  body  has  been  very  recently  discovered  by  Berthelot, 
who  obtained  it  in  the  pure  state  by  the  action  of  silent  elec- 
tric discharges  of  high  tension  upon  a  mixture  of  equal  vol- 
umes of  sulphurous  oxide  and  oxygen,  both  perfectly  dry. 
Persulphuric  oxide  is  formed,  and  there  remains  a  residue  of 
oxygen. 

S204        -f        O4  S207        -f        0 

4  vol.  sulphurous  oxide.      4  vol.  oxygen.         Persulphuric  oxide.  Oxygen. 

When  pure  it  is  solid  at  ordinary  temperatures,  crystallizing 
sometimes  in  grains,  sometimes  in  thin  and  flexible  transparent 
needles.  Sometimes  it  remains  liquid. 

It  is  not  stable,  and  decomposes  spontaneously  in  about  two 
weeks.  When  heated,  it  decomposes  rapidly  into  sulphuric 
oxide  and  oxygen. 

S207  2S03        -f        O 

Persulphuric  oxide.         Sulphuric  oxide. 

Water  dissolves  it  with  production  of  dense  fumes  and  a 
brisk  effervescence  due  to  the  disengagement  of  oxygen.  The 
liquid  then  contains  sulphuric  acid.  At  the  same  time  a  small 
quantity  of  persulphuric  acid,  H2S208,  or  HSO,  is  formed, 
which  soon  decomposes  into  sulphuric  acid  and  oxygen. 

This  persulphuric  acid,  which  is  very  unstable,  would  be 
analogous  to  permanganic  acid  ;  its  formation  is  expressed  by 
the  following  equation  : 

S'O7  -f-  H20  **  2HS04 


SELENIUM   AND   TELLURIUM.  Ill 

According  to  Berthelot,  persulphuric  acid  is  formed  by  the 
electrolysis  of  concentrated  solutions  of  sulphuric  acid.  It 
would  also  be  formed  by  the  careful  addition  of  a  solution 
of  hydrogen  dioxide  to  sulphuric  acid  slightly  diluted  with 
water. 

2H2S04  -f  0  =  H20  -f  2HSO 

It  is  by  no  means  certain  that  the  formula  HSO4  represents 
the  composition  of  a  molecule  of  persulphuric  acid.  It  is  pos- 
sible that  this  formula  must  be  doubled  as  indicated  above. 
At  present  this  point  cannot  be  decided. 


SELENIUM   AND   TELLURIUM. 

These  two  rare  elements  present  a  great  analogy  to  sulphur. 

Selenium  was  discovered  by  Berzelius  in  certain  Swedish 
pyrites.  Like  sulphur,  selenium  has  two  allotropic  forms,  one 
crystalline,  the  other  vitreous  and  amorphous.  The  crystalline 
variety  begins  to  melt  above  217°,  but  liquefies  only  at  250° 
(Regnault) ;  after  rapid  cooling  it  solidifies  into  a  dark-brown 
mass.  Its  density  is  4.8  when  crystallized,  and  4.3  when  vit- 
reous. When  heated  in  the  air  to  a  temperature  above  its 
melting-point  it  takes  fire  and  burns  with  a  blue  flame,  being 
converted  into  selenious  oxide,  SeO2.  When  sulphurous  acid 
is  added  to  a  solution  of  selenious  oxide  the  latter  is  reduced, 
sulphuric  acid  is  formed,  and  the  selenium  is  precipitated  in 
the  form  of  brown -red  flakes.  Its  compound  with  hydrogen 
is  a  colorless  gas  having  a  fetid  and  irritating  odor. 

Tellurium  is  still  more  rare  than  selenium ;  it  occurs  com- 
bined with  gold  and  other  metals  in  certain  minerals  of  Tran- 
sylvania and  Hungary,  and  also  in  the  Rocky  Mountain  gold 
region  in  the  United  States.  It  has  the  external  appearance 
and  the  lustre  of  a  metal.  Its  color  is  silvery-white  ;  its  den- 
sity 6.25.  It  melts  at  about  500°,  and  can  be  volatilized  at  a 
white  heat  in  a  current  of  hydrogen.  It  has  a  great  tendency 
to  crystallize.  When  heated  in  the  air  it  burns  with  a  green- 
ish-blue flame,  forming  tellurious  oxide,  TeO2.  Its  compound 
with  hydrogen  is  a  gas  having  an  odor  analogous  to  that  of 
hydrogen  sulphide. 

The  following  table  shows  the  analogy  between  the  principal 
compounds  of  sulphur,  selenium,  and  tellurium : 


112 


ELEMENTS   OF   MODERN   CHEMISTRY. 


H2S 

H2Se 

H2Te 

Hydrogen  sulphide. 

Hydrogen  selenide. 

Hydrogen  telluride. 

SO2 

SeO2 

TeO2 

Sulphurous  oxide. 

Selenious  oxide. 

Tellurious  oxide. 

SO3 

[SeO3] 

TeO3 

Sulphuric  oxide. 

Selenic  oxide. 

Telluric  oxide. 

[H2S03] 

H2Se03 

H2Te03 

Sulphurous  acid. 

Selenious  acid. 

Tellurious  acid. 

H2SO 

H2SeO* 

H'TeO4 

Sulphuric  acid. 

Selenic  acid. 

Telluric  acid. 

CHLORINE. 

Density  compared  to  air 2.44 

Density  compared  to  hydrogen 35.5 

Atomic  weight  Cl =  35.5 

Chlorine  was  discovered  by  Scheele  in  1774,  and  was  first 
recognized  as  an  element  by  G-ay-Lussac  and  Thenard  in  1809, 
and  by  Sir  Humphry  Davy  in  1810. 

Preparation. — One  part  of  manganese  dioxide  in  coarse 
powder  and  six  parts  of  common  hydrochloric  acid  are  intro- 


FIG.  38. 

duced  into  a  flask  fitted  with  a  safety-tube  and  delivery-tube 
(Fig.  38).     The  reaction  begins  in  the  cold ;  chlorine  gas  is 


CHLORINE. 


113 


disengaged,  and  may  be  collected  over  salt  water.  As  soon  as 
the  disengagement  of  gas  diminishes,  it  may  be  re-established 
by  the  application  of  a  gentle  heat. 

It  is  more  convenient  to  collect  the  gas  by  dry  displacement, 
and  it  may  be  obtained  pure  and  dry  by  being  conducted 
through  a  wash-bottle  containing  a  small  quantity  of  water,  and 
a  tube  containing  calcium  chloride,  as  represented  in  the  figure. 
It  is  then  passed,  by  means  of  a  tube  bent  at  a  right  angle, 
into  a  dry  jar.  The  chlorine  being  heavier  than  the  air,  col- 
lects at  the  bottom  of  the  jar  and  gradually  drives  out  the  air, 
and  the  uniform  greenish  color  of  the  whole  of  the  gas  in  the 
jar  indicates  when  the  latter  is  completely  filled. 

If  it  be  desired  to  prepare  a  solution  of  chlorine  in  water, 
the  gas  may  be  passed  through  a  series  of  Wolff's  bottles  con- 


FIG.  39. 

tain  ing  water,  the  contents  of  the  first  bottle  being  rejected, 
serving  merely  to  wash  the  gas  (Fig.  39). 

The  reaction  which  takes  place  in  the  preparation  of  chlo- 
rine is  a  double  decomposition  between  the  manganese  dioxide 
and  the  hydrochloric  acid.  Water  and  manganese  chloride 
are  formed,  and  chlorine  is  set  free. 

MnO2        -f       4HC1     ==  2H20  +     MnCP     +      Cl2 

Manganese  dioxide.        Hydrochloric  acid.  Manganese  chloride. 

Physical   Properties. — Chlorine  is  a  greenish-yellow  gas 
10* 


114  ELEMENTS    OF    MODERN    CHEMISTRY. 

having  a  strong  and  suffocating  odor.  A  litre  of  this  gas 
weighs  3.16  gr.  It  may  be  liquefied  at  15°  by  a  pressure  of 
four  atmospheres.  A  small  quantity  of  the  liquid  may  easily 
be  prepared  in  the  following  manner : 

Some  crystals  of  chlorine  hydrate  are  introduced  into  a  tube 
of  thick  glass  closed  at  one  end  and  bent  in  the  middle ;  the 

other  end  is  then  hermetically 
sealed  at  the  blast-lamp.  The 
branch  containing  the  crystals  is 
then  heated  in  a  water-bath,  while 
the  other  branch  is  cooled  in  a 
freezing  mixture  (Fig.  40).  The 
hydrate  of  chlorine  breaks  up 
into  water  and  chlorine,  and  the 
greater  part  of  the  latter  is  disen- 
gaged, and  condenses  by  its  own 
pressure  into  a  deep-yellow  liquid, 
which  collects  in  the  cooler  limb 
of  the  tube  (Faraday). 

Chemical  Properties. — One  volume  of  water  at  8°  dissolves 
3  volumes  of  chlorine  ;  at  17°,  2.42  volumes.  The  saturated 
solution  has  a  yellow  color.  When  it  is  exposed  to  a  tempera- 
ture of  0°,  it  deposits  crystals  containing  27.7  per  cent,  of 
chlorine,  and  72.3  per  cent,  of  water,  and  constituting  a  hydrate 
of  chlorine  corresponding  to  the  formula  CP  -\-  10H20  (Fara- 
day). 

Chlorine  possesses  powerful  affinities.  It  unites  directly 
with  the  greater  number  of  the  other  elements,  and  the  com- 
bination frequently  takes  place  with  such  energy  that  luminous 
heat  is  produced. 

Experiments. — If  powdered  antimony  or  arsenic  be  sprinkled 
into  a  jar  containing  dry  chlorine,  each  particle  of  the  black 
powder  burns  with  a  bright  spark  as  soon  as  it  enters  the  atmos- 
phere of  chlorine,  producing  thick,  white  fumes  of  antimony 
or  arsenic  chloride  as  the  case  may  be. 

If  a  morsel  of  phosphorus,  contained  in  a  deflagrating  spoon, 
be  plunged  into  a  jar  of  chlorine,  the  phosphorus  melts  and 
inflames  spontaneously,  and  the  sides  of  the  jar  become  covered 
with  a  yellow,  crystalline  deposit  of  phosphorus  pentachloride, 
PCI5. 

But  the  affinity  of  chlorine  is  most  strikingly  manifested  by 
its  action  on  hydrogen  and  hydrogen  compounds. 


CHLORINE.  115 

When  a  lighted  taper  is  applied  to  a  mixture  of  equal  vol- 
umes of  chlorine  and  hydrogen,  the  two  gases  unite  instantly 
and  explosively.  Such  a  mixture  will  also  explode  violently 
on  being  exposed  to  direct  sunlight ;  the  rays  of  the  sun  may 
even  be  replaced  by  the  flame  of  magnesium  or  that  of  carbon 
disulphide. 

So  great  is  the  affinity  of  chlorine  for  hydrogen  that  it  de- 
composes all  hydrogen  compounds,  except  hydrochloric  and 
hydrofluoric  acids.  When  it  is  dissolved  in  water,  it  slowly 
decomposes  that  liquid  under  the  influence  of  sunlight,  com- 
bining with  the  hydrogen  and  setting  the  oxygen  at  liberty. 

If  a  tube  filled  with  an  aqueous  solution  of  chlorine  be 
inverted  over  the  pneumatic  trough  and  exposed  to  direct  sun- 
light, small  bubbles  of  gas  will  be  seen  to  rise  through  the  liquid 
and  collect  at  the  top  of  the  tube.  This  is  the  oxygen  result- 
ing from  the  decomposition  of  the  water. 

At  a  red  heat,  the  vapor  of  water  is  rapidly  decomposed  by 
chlorine ;  hydrogen  sulphide  gives  up  its  hydrogen  to  chlorine 
at  ordinary  temperatures. 

All  organic  substances  contain  hydrogen ;  they  are  therefore 
generally  modified,  and  often  destroyed  by  the  action  of  chlorine. 
Coloring  matters  of  organic  origin  are  bleached. 

Experiment. — If  a  solution  of  chlorine  be  added  to  a  solu- 
tion of  litmus,  sulphate  of  indigo,  or  ink,  the  intense  colors 
peculiar  to  these  substances  disappear,  giving  place  to  a  pale 
yellow  or  brown  tint.  This  effect  is  due  to  the  more  or  less 
profound  decomposition  which  these  coloring  matters  undergo 
by  reason  of  the  removal  of  a  certain  portion  of  their  hydro- 
gen in  the  form  of  hydrochloric  acid. 

This  bleaching  property  of  chlorine  is  of  great  service  in  the 
arts. 

A  wax  taper  will  burn  in  chlorine  gas  with  a  red,  smoky 
flame.  The  hydrogen  of  the  wax  combines  with  the  chlorine, 
while  the  carbon  is  set  free  as  smoke.  A  piece  of  paper  satu- 
rated with  oil  of  turpentine  takes  fire  spontaneously  when 
introduced  into  a  jar  of  chlorine,  producing  a  dense  cloud  of 
smoke  ;  the  turpentine  contains  only  carbon  and  hydrogen  the 
latter  is  attacked  by  the  chlorine,  the  former  being  set  free. 

Chlorine  is  also  an  efficacious  disinfectant.  It  decomposes 
hydrogen  sulphide.  It  destroys  odorous  matters  of  organic 
origin,  the  effluvia  resulting  from  putrid  fermentation,  and 
the  miasms  which  are  sometimes  diffused  in  the  air.  It 


116  ELEMENTS    OF   MODERN    CHEMISTRY. 

is  employed  to  disinfect  privys,  etc.,  and  to  purify  the  air  in 
certain  epidemics. 

The  bleaching  properties  and  disinfecting  properties  of 
chlorine  are  due  to  the  same  cause, — its  powerful  affinity  for 
hydrogen. 

HYDROCHLORIC   ACID. 

Density  compared  to  air 1.247 

Density  compared  to  hydrogen 18. 

Molecular  weight  HC1 =  36.5 

Hydrochloric  acid  exists  among  the  gaseous  products  disen- 
gaged by  volcanoes. 


FIG. 


Preparation. — Fragments  of  fused  common  salt  are  intro- 
duced into  a  flask  fitted  with  a  safety-tube  and  delivery-tube, 
like  that  for  the  preparation  of  chlorine,  and  concentrated  sul- 
phuric acid  is  added.  Hydrochloric  acid  gas  is  disengaged,  and 


HYDROCHLORIC   ACID. 


117 


may  be  collected  over  mercury.    Sodium  acid  sulphate  remains 
in  the  retort. 


H2S04 


+     NaCl      =      NaHSO*     +     HC1 

Sodium  chloride.      Sodium  acid  sulphate. 


In  the  arts,  the  operation  is  conducted  in  cast-iron  cylinders 
or  furnaces  (Fig.  41),  at  a  high  temperature.  Under  these 
conditions,  one  molecule  of  sulphuric  acid  acts  upon  two  mole- 
cules of  sodium  chloride,  yielding  sodium  neutral  sulphate, 
and  two  molecules  of  hydrochloric  acid. 

H'SO4     -f     2NaCl     =     Na2S04     +     2HC1 

Sodium  sulphate. 

The  hydrochloric  acid  gas  evolved  is  passed  into  stoneware 
bottles,  C,  C',  C'',  containing  water.  It  is  thus  dissolved, 
and  the  solution  obtained  constitutes  the  muriatic  acid  of  com- 
merce. 

A  solution  of  hydrochloric  acid  may  be  prepared  in  the 
laboratory  by  passing  the  gas  through  water  contained  in  a 
series  of  Wolff  bottles  surrounded  by  cold  water,  the  contents 
of  the  first  bottle  being  rejected  (Fig.  42). 


FIG.  42. 


Composition  of  Hydrochloric  Acid. — The  composition  of 
this  gas  may  be  deduced  from  the  following  experiments : 


118 


ELEMENTS    OF    MODERN    CHEMISTRY. 


FIG.  43. 


1.  A  bottle,  B  (Fig.  43),  the  neck  of  which  is  adapted  by 
grinding  with  emery  to  the  flask  A,  is  filled  with  dry  chlorine ; 

A,  which  has  exactly  the  same  capacity  as 
the  bottle,  is  filled  with  dry  hydrogen  ;  the 
two  vessels  are  then  fitted  together,  and  by 
means  of  the  ground  joint  are  hermetically 
sealed.  The  apparatus  is  now  abandoned 
for  a  time  to  diffuse  light,  and  as  the  two 
gases  slowly  mix  they  combine.  The  union 
is  completed  by  exposing  the  apparatus  to 
direct  sunlight.  When  the  tint  of  the 
chlorine  has  entirely  disappeared,  the  two 
vessels  are  separated  under  the  surface  of 
mercury,  and  it  is  found  that  no  change  in 
volume  has  taken  place.  The  chlorine  and 
hydrogen  have  both  disappeared  to  form 
hydrochloric  acid,  which  occupies  precisely 
the  same  volume  as  the  two  primitive  gases.  Consequently  2 
volumes  of  hydrochloric  gas  contain  1  volume  of  chlorine  and 
1  volume  of  hydrogen ;  and  if  the  weight  of  one  volume  of 
hydrogen  (unity)  be  added  to  that  of  one  volume  of  chlorine 
(its  density  compared  to  hydrogen  as  unity),  the  sum  will  be 
the  weight  of  two  volumes  of  hydrochloric  acid,  and  will  also 
represent  the  weight  of  the  molecule. 

Densities  com-  Densities  com- 
pared to  H.  pared  to  Air. 

Weight  of  1  volume  of  hydrogen  ....     1  0.0693 

Weight  of  1  volume  of  chlorine     ....  35.5  2.44 

Weight  of  2  volumes  of  hydrochloric  acid     3(K5  2.5093 

2.  Two  volumes  of  hydrochloric  acid  gas  are  passed  into  a 
bent  tube  over  mercury  (Fig.  44),  and  a  small  piece  of  sodium 

is  passed  up  into  the  bulb  and 
heated  by  the  flame  of  a  spirit- 
lamp.  The  sodium  combines 
with  the  chlorine  setting  the 
hydrogen  at  liberty,  and  after 
the  experiment  one  volume  of 
hydrogen  remains  in  the  tube. 
This  second  experiment  con- 
firms the  first,  both  proving 
that  hydrogen  and  chlorine 
unite  in  equal  volumes,  and 
without  condensation,  to  form 


FIG.  44. 


HYDROCHLORIC    ACID. 


119 


hydrochloric  acid.  One  volume  of  hydrochloric  acid  contains 
half  a  volume  of  hydrogen  and  half  a  volume  of  chlorine,  but 
we  cannot  admit  that  the  atoms  of  these  elements  are  divided 
into  two  in  the  formation  of  hydrochloric  acid ;  such  a  sup- 
position would  be  contrary  to  all  ideas  of  atoms,  which  repre- 
sent the  smallest  particles  of  an  element  that  can  exist  in  a 
compound.  It  is  more  natural  to  conclude  that  two  vol- 
umes of  chlorine  and  two  volumes  of  hydrogen  react  together 
in  the  formation  of  hydrochloric  acid.  Two  volumes  of 
chlorine  contain  two  atoms,  constituting  one  molecule  of  chlo- 
rine. In  the  same  manner  two  volumes  of  hydrogen  contain 
two  atoms,  constituting  one  molecule  of  hydrogen. 


Cl 


Cl 


H 

H 

volumes  or  1  molecule  of 
chlorine  =  CNJ1. 


2  volumes  or  1  molecule  of 
hydrogen  =  HH. 


It  is  these  molecules  which  are  separated  into  two  when 
chlorine  combines  with  hydrogen :  they  exchange  their  atoms, 
and  from  the  exchange,  which  is  a  double  decomposition,  there 
result  two  molecules  of  hydrochloric  acid,  which  occupy  pre- 
cisely the  same  volume  as  the  two  molecules  of  the  simple  gases. 


Cl     Cl 


H      H     =     H     Cl 


H      Cl 


2  vols.  of  chlorine  +  2  vole,  of  hydrogen  r=  2  vols.  of  hydro-  +  2  vola.  of  hydro- 
chloric acid  chloric  acid. 

We  encounter  here  again  the  notion  that  certain  elements  in 
the  free  state  are  composed  of  molecules,  each  of  which  con- 
tains two  atoms  of  the  same  kind.  The  force  which  unites 
them  is  not  different  from  affinity.  It  is  affinity  which  unites 
chlorine  to  chlorine  in  the  molecule  of  that  element ;  hydrogen 
to  hydrogen  in  the  molecule  of  free  hydrogen  (Gerhardt). 
When,  however,  these  two  molecules  are  brought  together,  the 
affinity  of  chlorine  for  hydrogen  preponderates,  and  brings  about 
an  exchange,  a  double  decomposition. 

Physical  Properties. — Hydrochloric  acid  is  a  colorless  gas 
having  a  pungent  odor.  It  forms  thick  white  fumes  in  the  air 
by  condensing  the  atmospheric  moisture.  It  may  be  liquefied 
by  a  pressure  of  40  atmospheres. 

It  is  one  of  the  most  soluble  of  gases  in  water.  If  a  jar 
filled  with  this  gas  and  inverted  on  a  plate  containing  mercury 


120  ELEMENTS   OF   MODERN   CHEMISTRY. 

so  that  the  mouth  is  sealed,  be  depressed  in  the  pneumatic 
trough,  and  the  plate  be  then  quickly  removed,  the  water  im- 
mediately rushes  into  the  jar  as  it  would  into  a  vacuum.  The 
shock  of  the  column  of  water  is  sometimes  sufficient  to  break 
the  jar. 

One  volume  of  water  at  0°  dissolves  500  volumes  of  hydro- 
chloric acid;  at  ordinary  temperatures,  about  480  volumes. 
The  water  becomes  heated  and  increases  in  volume.  The  cold 
saturated  solution  has  a  density  of  1.21  and  contains  42.4 
per  cent,  by  weight  of  the  dry  gas.  It  is  a  colorless  liquid, 
giving  off  white  fumes.  When  it  is  heated,  it  loses  a  large 
quantity  of  the  gas  which  it  holds  in  solution,  but  the  whole 
of  the  gas  is  not  disengaged,  and  when  the  temperature  reaches 
110°  the  liquid  distils  without  further  loss  of  gas.  A  dilute 
hydrochloric  acid  is  thus  obtained,  having  a  uniform  density  of 
1.10  (Bineau). 

Chemical  Properties. — Hydrochloric  acid  is  an  energetic 
acid ;  it  strongly  reddens  litmus-paper.  It  is  not  decomposable 
by  heat,  but  is  partly  decomposed  by  a  series  of  electric  sparks. 
AH  of  the  metals  which  decompose  water  also  decompose  hy- 
drochloric acid  with  the  liberation  of  hydrogen  and  the  for- 
mation of  a  chloride.  Such  metals  are  sodium,  zinc,  iron, 
aluminium,  tin,  etc. 

Hydrochloric  acid  decomposes  the  metallic  oxides  and  hy- 
drates with  the  formation  of  water  and  a  chloride. 

If  hydrochloric  acid  be  added  in  small  quantities  to  a  con- 
centrated solution  of  potassium  hydrate,  the  liquid  becomes 
heated  and  deposits  potassium  chloride  as  a  crystalline  powder. 

HC1      -f      KOH      =      KC1      -f      H2O 

Potassium  hydrate.    Potassium  chloride. 

Hydrochloric  acid  is  then  a  true  acid  although  it  contains  no 
oxygen,  for  it  contains  an  atom  of  hydrogen  that  is  replaceable 
by  an  atom  of  metal.  In  its  action  upon  potassium  hydrate  it 
resembles  nitric  acid,  for  this  acid  also  contains  one  atom  of 
hydrogen,  which  is  replaceable  by  an  atom  of  metal. 

HNO3     -f     KOH     =     KNO3     -f     H20 

Nitric  acid.  Potassium  nitrate. 

It  is  seen  that  the  acids  are  compounds  containing  a  strongly 
electro-negative  atom  or  group  of  atoms,  united  with  hydrogen, 
which  hydrogen  can  be  replaced  by  a  metal.  In  nitric  acid, 
H(N03),  the  group  NO3  plays  the  part  taken  by  chlorine  in 


OXYGEN   COMPOUNDS   OF   CHLORINE. 


121 


hydrochloric  acid ;  like  the  chlorine,  it  renders  the  hydrogen 
replaceable  by  a  metal. 

The  action  of  hydrochloric  acid  upon  the  metallic  oxides  is 
analogous  to  that  which  it  exerts  upon  the  hydrates. 

If  a  current  of  hydrochloric  acid  be  passed  over  mercuric 
oxide  contained  in  a  tube  (Fig.  45),  the  oxide  becomes  heated, 


O— 


FIG.  45. 

and  is  converted  into  a  white  powder  which  is  mercuric  chlo- 
ride ;  at  the  same  time  water  is  formed  and  condenses  in  the 
bulb. 

HgO     +     2HC1    =    HgCP     +     H20 


Mercuric  oxide. 


Mercuric  chloride. 


OXYGEN  COMPOUNDS  OF   CHLORINE. 

With  oxygen,  chlorine  forms  compounds  which  may  be  an- 
hydrous or  hydrated  ;  the  latter  are  acids. 
The  oxides  are : 

Hypochlorous  oxide C120 

Chlorous  oxide C1203 

Chlorine  peroxide C120* 

The  acids  are : 

Hypochlorous  acid HC10 

Chlorous  acid HC102 

Chloric  acid HC103 

Perchloric  acid HC104 

F  11 


122 


ELEMENTS   OF   MODERN   CHEMISTRY. 


HYPOCHLOROUS   OXIDE   AND   ACID. 

Hypochlorous  oxide  is  prepared  by  passing  a  current  of  dry 
chlorine  over  mercuric  oxide  contained  in  a  tube  surrounded 
by  cold  water,  and  may  be  condensed  in  a  long-necked  matrass 
placed  in  a  freezing  mixture  (Fig.  46). 

HgO     -f     2CP     ==     HgCP     -f     CPO 

Mercuric  oxide.  Mercuric  chloride. 


FIG.  46. 

The  oxide  condenses  as  a  brown-red  liquid,  boiling  at  20°. 
Above  that  temperature  it  is  a  reddish-yellow  vapor,  having  a 
density  of  2.977,  or,  compared  to  hydrogen  as  unity,  43.5. 
Two  volumes  of  this  vapor  contain  two  volumes  of  chlorine 
and  one  volume  of  oxygen,  a  composition  represented  by  the 
formula  CPO. 

Hypochlorous  oxide  is  a  dangerous  body,  and  cannot  be  kept 
for  more  than  a  few  hours  without  spontaneous  decomposition  ; 
its  vapor  frequently  explodes. 

In  combining  with  the  elements  of  water,  hypochlorous  oxide 
forms  hypochlorous  acid,  the  solution  of  which  is  almost  color- 
less. 


ci 


+ 


H 


ci 


+ 


H 


CHLOROUS   OXIDE.  123 

Preparation  of  Hypochlorous  Acid. — 1.  A  solution  of 
hypochlorous  acid  may  be  prepared  by  agitating  mercuric 
oxide  with  water  in  jars  filled  with  chlorine  gas.  The  water 
will  then  contain  hypochlorous  acid  and  mercuric  chloride,  and 
there  remains  a  brown  powder,  which  is  mercury  oxychloride 
(Balard). 

2.  A  current  of  chlorine  is  passed  through  water  holding 
recently-precipitated  calcium  carbonate  in  suspension.  The 
latter  disappears,  carbonic  acid  gas  is  disengaged,  and  the 
water  becomes  charged  with  calcium  chloride  and  hypochlorous 
acid.  The  mixture  is  distilled,  and  the  acid  which  passes  with 
the  water  is  condensed  in  a  cooled  receiver  (Williamson). 

CaCO3  +  2CP  +  H20  ==  CO2  +  CaCP  +    2HC10 

Calcium  Carbon          Calcium         Hypochlorous 

carbonate.  dioxide.         chloride.  acid. 

Properties  of  Hypochlorous  Acid. — Concentrated  hypo- 
chlorous  acid  is  a  dark-yellow  liquid,  having  the  peculiar  smell 
of  chlorinated  lime  or  bleaching-powder.  It  is  very  caustic, 
and  rapidly  destroys  the  skin  ;  its  bleaching  power  is  very  en- 
ergetic, double  that  of  the  chlorine  it  contains.  Hydrochloric 
acid  decomposes  it  into  chlorine  and  water. 

HC10  +  HC1  =  CP  +  H2O 
CHLOROUS   OXIDE. 


Chlorous  oxide  is  formed  when  potassium  chlorate  is  decom- 
posed by  dilute  nitric  acid  in  the  presence  of  a  body  capable 
of  uniting  with  oxygen,  such  as  arsenious  oxide.  At  a  gentle 
heat  a  greenish  gas  is  disengaged  which  does  not  liquefy  at  a 
temperature  of — 20°.  This  gas  is  not  stable;  above  57°  it 
decomposes  with  explosion  into  chlorine  and  oxygen. 

It  dissolves  in  water,  forming  a  dark  golden-yellow  solution 
containing  chlorous  acid,  a  body  quite  unstable  itself. 

CPO3      +       H20      =      2HC102 

Chlorous  oxide.  Chlorous  acid. 


124 


ELEMENTS    OF    MODERN    CHEMISTRY. 


CHLORINE   PEROXIDE. 


Fia.  47. 


This  compound,  which  was 
discovered  by  Sir  Humphry 
Davy,  is  prepared  by  the  ac- 
tion of  concentrated  sulphuric 
acid  upon  fused  potassium 
chlorate.  The  salt  is  finely 
pulverized  arid  added  in  small 
quantities  to  sulphuric  acid 
cooled  to  — 10°.  The  pasty 
mass  is  then  introduced  into 
a  small  test-tube  fitted  with  a 
delivery-tube  (Fig.  47),  and 
is  gently  heated  in  a  water- 
bath  ;  the  gas  disengaged  is 
collected  in  dry  jars  by  down- 
ward displacement. 

3KC103  +  2H2SO*  ±=  KC10*  +  2KHSO*  +  H20  +  CPO* 

Potassium  Potassium       Potassium  acid 

chlorate.  perchlorate.  sulphate. 

Chlorine  peroxide  is  a  yellow  gas  having  a  sweetish  aromatic 
odor.  At  — 20°  it  condenses  to  an  orange-red  liquid.  Its  den- 
sity in  the  gaseous  state  is  33.75  (hydrogen  being  unity).  This 
density  is  anomalous,  and  indicates  that  at  the  instant  the  liquid 
CPO*  assumes  the  gaseous  state  it  is  dissociated  into  two  more 
simple  molecules,  CIO2  -f-  CIO2,  which  occupy  four  volumes. 

is  resolved  into 

j f  j 

The  density  of  gaseous  chlorine  peroxide  is  then  only  half 
that  required  by  the  formula  CPO*. 

If  one  volume  of  hydrogen  weighs 

one  volume  of  C1204  ought  to  weigh 

But  it  weighs  only oo.i./, 

which  proves  that  CPO*  in  the  gaseous  state  occupies 
volumes  instead  of  two. 

These  four  volumes  contain,  2  volumes  of  Cl,  weighing  2  X  35.5  =    71 
4  volumes  of  0,  weighing  16  X    4     ==  J54 

135 


Cl2 

0* 

Cl 

O2 

Cl 

O2 

1, 

67.5. 
33.75 


four 


Weight  of  one  volume,  or  density,  compared  to  H 


-!L'_    33.75 


CHLORIC   ACID — PERCHLORIC   ACID.  125 

Chlorine  peroxide  is  a  dangerous  body;  it  sometimes  de- 
composes spontaneously  with  violent  explosions. 

It  is  soluble  in  water,  and  the  solution  may  be  prepared  by 
heating  on  a  water-bath  a  mixture  of  equal  parts  of  oxalic  acid 
and  potassium  chlorate.  Carbonic  acid  and  chlorine  peroxide 
gases  are  disengaged,  and  may  be  passed  into  water. 

Chlorine  peroxide  is  absorbed  by  alkaline  solutions  with  the 
formation  of  a  chlorate  and  a  chlorite. 

2KOH      -f  CFO  ==      KC103      +       KC10*  +  IPO 

Potassium  hydrate.  Potassium  chlorate.    Potassium  chlorite. 


CHLORIC  ACID. 
HC103 

This  acid  is  formed  by  the  spontaneous  decomposition  of 
solutions  of  hypochlorous  and  chlorous  acids  and  chlorine  per- 
oxide. 

It  may  be  prepared  by  treating  barium  chlorate  with  dilute 
sulphuric  acid.  Barium  sulphate  precipitates,  and  is  removed 
by  filtration,  and  the  solution  of  chloric  acid  is  concentrated  by 
evaporation  in  vacuo. 

Chloric  acid  is  a  syrupy  liquid,  ordinarily  of  a  yellow  color ; 
it  is  not  very  stable ;  at  a  temperature  of  40°  it  commences  to 
decompose,  and  at  a  higher  temperature  it  is  resolved  into  per- 
chloric acid,  chlorine,  oxygen,  and  water.  It  has  extremely 
energetic  oxidizing  properties ;  when  concentrated,  it  at  once 
inflames  sulphur,  phosphorus,  alcohol,  and  paper.  It  oxidizes 
sulphurous  and  phosphorous  acids  and  hydrogen  sulphide. 
With  hydrochloric  acid  it  forms  water  and  chlorine. 

HC103  +  5HC1  =  3H20  +  3CP 


PERCHLORIC    ACID. 
HC10* 

This  is  the  most  rich  in  oxygen  of  all  the  chlorine  acids, 
and  it  is  a  curious  circumstance  that  it  is  also  the  most  stable. 

It  may  be  prepared  by  distilling  potassium  perchlorate  with 
concentrated  sulphuric  acid.  Roscoe  obtains  it  by .  distilling 
chloric  acid,  which  is  prepared  by  decomposing  a  solution  of 
potassium  chlorate  by  hydrofluosilicic  acid.  The  insoluble  po- 
ll* 


126  ELEMENTS    OF    MODERN    CHEMISTRY. 

tassium  fluosilicate  is  separated  by  filtration,  the  filtered  liquid 
is  concentrated  until  white  fumes  appear,  and  then  the  distil- 
lation is  commenced.  The  product  must  be  rectified  after 
being  freed  from  the  chlorine  which  is  formed  at  the  same 
time. 

The  perchloric  acid  thus  obtained  is  a  heavy,  oily,  colorless 
liquid,  resembling  concentrated  sulphuric  acid.  It  still  con- 
tains water,  which  may  be  removed  by  distillation  with  four 
times  its  weight  of  concentrated  sulphuric  acid.  At  about 
100°  dense  vapors  pass  and  condense  into  a  very  mobile,  yellow 
liquid ;  this  is  the  perchloric  acid  HC104 ;  the  temperature 
then  rises,  and  at  200°  a  liquid  passes  which  solidifies  to  a 
crystalline  mass  on  cooling.  These  crystals  are  a  hydrate, 
HC10*  +  H20. 

The  pure  or  normal  perchloric  acid  has  a  density  of  1.782 
at  15.5°.  When  brought  into  contact  with  water,  it  combines 
with  that  liquid,  producing  a  hissing  noise.  Its  oxidizing 
powers  are  so  energetic  that  it  explodes  on  contact  with  paper, 
wood,  or  charcoal.  It  may  be  mixed  with  alcohol,  but  with 
ether  it  explodes.  It  cannot  be  distilled.  The  hydrate 
HC10*  -f  H20  melts  between  50  and  51°. 

CHLORIDES   OF   SULPHUR. 

When  a  current  of  dry  chlorine  is  passed  over  sulphur  heated 
in  a  retort,  a  liquid  condenses  in  the  receiver  which  fumes  in 
the  air,  has  a  yellow  color,  and  an  irritating,  fetid  odor.  This 
is  sulphurous  chloride,  S2CF.  In  order  that  this  compound 
may  be  formed,  the  sulphur  must  be  maintained  in  excess,  and 
the  operation  must  be  stopped  before  it  has  all  disappeared. 
The  product  is  purified  by  rectification,  that  part  being  collected 
which  passes  at  139°. 

When  chlorine  is  passed  for  several  hours  through  the 
chloride  of  sulphur  just  described,  the  yellow  color  of  the 
latter  changes  to  deep  red.  The  liquid  obtained  is  mobile, 
fumes  in  the  air,  and  continually  disengages  chlorine.  It  can- 
not be  distilled  without  decomposition.  The  product  which 
passes  is  at  first  red,  but  afterwards  assumes  a  lighter  color,  and 
when  the  temperature  reaches  139°  there  remains  in  the  retort 
only  sulph*urous  chloride,  S2C12. 

The  red  liquid  has  a  composition  which  corresponds  to  the 
formula  S2C14.  It  is  called  perchloride  of  sulphur.  Carius 


BROMINE.  127 

regards  it  as  a  mixture  of  the  chloride  S2CP  with  a  tetra- 
chloride  SCI4,  corresponding  to  sulphurous  oxide. 

SO2  sulphur  dioxide. 
SCI*  sulphur  tetrachloride. 

This  tetrachloride  has  been  recently  isolated  by  Michaelis, 
but  it  can  only  exist  at  a  low  temperature ;  it  decomposes  into 
chlorine  and  sulphurous  chloride,  S2CP,  as  soon  as  it  is  removed 
from  the  freezing  mixture  where  it  has  been  condensed. 

The  chlorides  of  sulphur  are  employed  in  vulcanizing 
caoutchouc. 


BROMINE. 

Vapor  density  compared  to  air     .     .     .       5.393 

Vapor  density  compared  to  hydrogen     .     77.9  (nearly  80) 

Atomic  weight  Br =80. 

Bromine  was  discovered  by  Balard  in  1826. 

Preparation. — It  is  obtained  by  decomposing  potassium 
bromide  by  manganese  dioxide  and  sulphuric  acid.  Potassium 
sulphate  and  manganese  sulphate  are  formed,  and  the  bromine 
is  liberated. 

2KBr  -f  MnO2  +  2H2S04  =  K'SO*  -f  MnSO*  +  2H20  +  Br2 

Potassium  Manganese  Potassium      Manganese 

bromide.      dioxide.  sulphate.         sulphate. 

The  operation  is  conducted  in  a  tubulated  retort,  heated  on 
a  sand-bath,  and  the  bromine  is  condensed  in  a  cooled  receiver 
fitted  to  the  retort  by  the  aid  of  an  adapter. 

The  potassium  bromide  may  be  replaced  by  magnesium 
bromide,  which  exists  in  the  mother-liquors  of  salt-springs. 
In  this  case  magnesium  sulphate  is  formed.  The  mother- 
liquors  of  the  soda  varech  from  which  the  iodine  has  Jbeen  ex- 
tracted are  also  employed  for  the  preparation  of  bromine. 

Properties. — Bromine  is  a  dark-red  liquid,  which  solidifies 
at  —7.3°.  Its  density  at  15°  is  2.99.  It  boils  at  63°,  and  at 
ordinary  temperatures  gives  off  red,  irritating  vapors,  for  its 
vapor  tension  is  considerable  even  in  the  cold.  It  stains  the 
skin  yellow,  and  immediately  corrodes  the  tissues.  It  dissolves 
in  about  33  times  its  weight  of  water  at  15°,  forming  an  orange- 
red  solution.  At  a  low  temperature  it  combines  with  water, 
forming  a  crystalline  hydrate,  Br2  -j-  10H20,  analogous  to  that 
formed  by  chlorine. 


128  ELEMENTS   OF   MODERN   CHEMISTRY. 

Bromine  dissolves  in  carbon  disulphide,  in  chloroform,  and  in 
ether. 

Experiment.  —  A  small  quantity  of  solution  of  potassium 
bromide  is  introduced  into  a  long  tube,  closed  at  one  end,  and 
the  tube  is  then  nearly  filled  with  chlorine-  water  ;  when  the  two 
solutions  are  mixed,  the  liquor  assumes  an  orange-red  color 
from  the  liberation  of  the  bromine.  The  tube  is  now  filled  up 
with  ether  and  agitated  briskly,  the  open  end  being  closed  with 
the  finger.  The  ether  passes  through  the  aqueous  solution 
and  dissolves  out  all  of  the  bromine,  assuming  at  the  same  time 
a  dark-red  color. 

The  affinity  of  bromine  for  hydrogen  is  powerful,  but  not  as 
energetic  as  that  of  chlorine.  Like  chlorine,  it  has  remarkable 
bleaching  properties. 

HYDROBROMIC  ACID. 

Density  compared  to  air   .........      2.73 

Density  compared  to  hydrogen       ......     40.5 

Molecular  weight  HBr      ........    =81. 

Preparation.  —  This  gas  is  prepared  by  the  action  of  water 
upon  phosphorus  tribromide. 


PBr3  8o»     ==        303     +       3HBr 

Phosphorus  tribromide.    3  molecules  water.    Phosphorous  acid. 

The  operation  may  be  conveniently  conducted  in  a  doubly- 
curved  tube  (Fig.  48).  Into  the  long  branch  CD  fragments  of 
phosphorus  are  introduced,  carefully  separated  from  each  other 
by  moistened  broken  glass.  The  bromine  is  introduced  into 
the  bend  A.  The  shorter  end  is  then  corked,  a  delivery-tube 
adapted  to  the  end  D,  and  the  bromine  is  gently  heated  until  it 
boils.  The  vapor  comes  into  contact  with  the  phosphorus  and 
forms  phosphorus  tribromide,  but  this  is  at  once  decomposed 
by  the  water  into  phosphorous  acid  and  hydrobromic  acid. 
The  latter  may  be  collected  in  jars  over  the  mercury-trough. 

Amorphous  phosphorus  may  be  advantageously  employed  in 
this  operation,  and  the  process  conducted  as  directed  for  hydri- 
odic  acid  (Personne). 

Properties.  —  Hydrobromic  acid  is  a  colorless  gas,  producing 
dense  white  fumes  in  the  air.  A  litre  of  this  gas  weighs  3.547 
grammes.  It  liquefies  at  —  73°,  and  may  be  solidified  at  a 
lower  temperature.  It  is  formed  by  the  union  of  equal  volumes 


OXYGEN   ACIDS   OF   BROMINE. 


129 


of  bromine  vapor  and  hydrogen  without  condensation,  so  that 
its  composition  corresponds  to  that  of  hydrochloric  acid.  It 
is  very  soluble  in  water ;  its  concentrated  solution  fumes  in  the 
air,  and  is  very  corrosive. 

Chlorine   decomposes   hydrobromic   acid,  setting   free   the 
bromine. 


Jb'io. 

OXYGEN   ACIDS   OF   BROMINE. 

There  are  known  three  bromine  oxygen  acids : 

Hypobromous  acid,  HBrO. 
Bromic  acid,  HBrO3. 
Perbromic  acid,  HBrO4. 

They  correspond  to  hypochlorous,  chloric,  and  perchloric 
acids. 

Hypobromous  Acid,  HBrO. — When  mercuric  oxide  is 
agitated  with  an  aqueous  solution  of  bromine,  a  yellowish 
liquid  is  obtained  which  contains  hypobromous  acid,  and  can 
be  distilled  in  vacuo.  W.  Dancer  has  obtained  this  acid  by  the 
action  of  bromine  upon  silver  oxide  suspended  in  water. 

2Br*     +     Ag20     -f     H20     =     2AgBr     -f-     2HBrO 

Silver  oxide.  Silver  bromide. 

In  this  process  it  is  necessary  to  operate  rapidly  and  avoid 


130  ELEMENTS   OF   MODERN   CHEMISTRY. 

the  contact  of  an  excess  of  silver  oxide  with  the  hypobromous 
acid,  as  the  latter  would  be  destroyed  by  the  oxide  with  evolu- 
tion of  oxygen. 

2HBrO  -f  Ag2O  =  2AgBr  +  H20  -f  O2 

The  solution  of  hypobromous  acid  has  a  yellow  color  and 
bleaching  properties  analogous  to  those  of  hypochlorous  acid. 

Bromio  Acid,  HBrO3. — Potassium  bromide  and  potassium 
bromate  are  formed  by  the  action  of  bromine  upon  a  concen- 
trated solution  of  potassium  hydrate.  This  reaction  is  similar 
to  that  of  chlorine  upon  potassa. 

Kammerer  recommends  the  preparation  of  bromic  acid  by 
the  action  of  chlorine  upon  bromine  in  presence  of  water. 

5CP  +  Br2  -f  6H2O  =  10HC1  -f-  2HBr03 

The  hydrochloric  acid  is  driven  out  by  evaporation,  and 
bromic  acid  remains  in  the  form  of  a  liquid  that  cannot  be  con- 
centrated to  a  syrupy  consistence  without  partial  decomposition. 

Perbromic  Acid,  HBrO4. — Kammerer  has  obtained  this 
acid  by  decomposing  perchloric  acid  with  bromine  :  chlorine  is 
disengaged.  After  concentration  on  a  water-bath,  the  per- 
bromic  acid  remains  as  a  colorless  oily  liquid.  It  is  relatively 
stable,  as  are  the  corresponding  chlorine  and  iodine  acids.  Like 
them,  it  resists  the  reducing  action  of  sulphurous  acid  and 
hydrogen  sulphide. 


IODINE.    • 

Vapor  density  compared  to  air     ...         8.716 

Vapor  density  compared  to  hydrogen    .     125.1  (nearly  127) 

Atomic  weight  I =  127. 

Iodine  was  discovered  by  Courtois  in  1811,  and  was  studied 
by  G-ay-Lussac  in  1813  and  1814. 

Natural  State. — Iodine  is  widely  disseminated  in  nature. 
It  is  found  in  the  mineral  kingdom  combined  with  various 
metals,  such  as  potassium,  sodium,  calcium,  magnesium,  silver, 
mercury.  The  alkaline  iodides  exist  in  small  quantity  in  sea- 
water,  in  a  great  number  of  salt-springs,  and  in  certain  rock- 
salts.  The  sodium  nitrate  found  native  in  Chili  contains  traces 
of  sodium  iodate,  and  the  mother-liquors  from  which  the  nitrate 
has  been  deposited  contain  enough  iodate  to  be  profitably 
employed  for  the  preparation  of  iodine.  The  ashes  of  certain 


IODINE.  131 

sea-plants,  such  as  the  algse  and  fuel,  are  the  most  abundant 
sources  of  iodine. 

Preparation. — The  ashes  of  sea-weeds,  called  kelp,  are  ex- 
hausted with  water  and  the  solution  concentrated.  Various 
salts,  such  as  sodium  and  potassium  sulphates  and  chlorides 
and  sodium  carbonate,  are  deposited,  and  the  potassium  iodide, 
which  is  contained  in  smaller  quantity  than  these  salts,  remains 
in  the  mother-liquor. 

A  regulated  current  of  chlorine  is  passed  into  this  solution 
as  long  as  it  continues  to  set  free  iodine,  which  is  deposited  as 
a  pulverulent,  black  precipitate.  An  excess  of  chlorine  must 
be  avoided,  as  this  would  redissolve  a  portion  of  the  iodine, 
forming  iodine  chloride. 

Another  process  consists  in  mixing  the  mother-liquor  with 
ordinary  nitric  acid  and  gently  heating  the  mixture.  The  alka- 
line iodide  is  decomposed  by  the  acid,  a  nitrate  is  formed,  red 
vapors  are  disengaged,  and  iodine  is  set  free. 

4HN03   +    2KI  =   2KN03   -f    2N02   +    2H20   +    I2 

Nitric  Potassium          Potassium  Nitrogen 

acid.  iodide.  nitrate.  peroxide. 

The  precipitated  iodine  is  collected,  drained,  and  after  drying 
is  sublimed  in  stoneware  vessels. 

The  same  process  that  has  been  described  for  the  manufacture 
of  bromine  from  potassium  bromide  may  also  be  applied  for  the 
extraction  of  iodine.  It  consists  in  treating  the  iodide  with 
manganese  dioxide  and  sulphuric  acid. 

Properties  of  Iodine. — The  iodine  obtained  by  sublimation 
occurs  as  scales  or  crystalline  plates,  having  a  brilliant,  dark 
bluish-gray  surface,  and  a  density  of  4.948  at  17°.  It  may  be 
obtained  crystallized  in  rhombic  octahedra  by  exposing  to  the 
air  a  solution  of  hydriodic  acid. 

Iodine  melts  at  107°.  It  boils  at  about  175°,  but  volatilizes 
sensibly  at  ordinary  temperatures.  Its  vapor  has  an  intense 
rich  violet  color.  A  litre  of  this  vapor  weighs  11.32  grammes. 

Iodine  is  but  very  slightly  soluble  in  water ;  one  part  of 
iodine  requires  7000  parts  of  water  for  its  solution,  but  com- 
municates a  light-brown  color  to  the  whole  of  that  liquid. 
Alcohol  and  ether  dissolve  iodine  freely,  forming  dark-brown 
solutions.  Carbon  disulphide,  benzine,  and  chloroform  also 
dissolve  it,  assuming  a  beautiful  violet  color. 

Experiment. — If  a  few  drops  of  chlorine-water  be  added  to 
a  very  dilute  solution  of  potassium  iodide,  the  chlorine  will 


132  ELEMENTS    OF    MODERN    CHEMISTRY. 

combine  with  the  potassium,  displacing  the  iodine,  which  will 
color  the  liquid  brown ;  if  now  the  solution  be  agitated  with  a 
small  quantity  of  chloroform,  the  latter  will  take  up  all  of  the 
iodine,  assuming  a  violet  color. 

Iodine  strikes  an  intense  blue  color  with  starch.  The  reac- 
tion is  very  delicate  and  permits  the  detection  of  the  smallest 
trace  of  free  iodine. 

Experiment. — If  a  few  drops  of  a  solution  of  potassium, 
iodide  be  added  to  a  solution  of  starch,  no  coloration  takes 
place,  because  the  iodine  is  in  combination ;  but  if  a  drop  or 
two  of  chlorine-water  be  added,  the  iodine  will  be  set  free,  and 
combining  with  the  starch  will  at  once  produce  the  character- 
istic blue  color.  An  excess  of  chlorine  will  again  destroy  the 
color. 

HYDRIODIC  ACID. 

Density  compared  to  air 4.443 

Density  compared  to  hydrogen        64.1 

Molecular  weight  HI =128. 

Preparation. — Hydriodic  acid  is  prepared  by  the  action  of 
iodine  upon  phosphorus  in  presence  of  water;  phosphorus 
triiodide  is  first  formed,  and  this  is  decomposed  into  phos- 
phorous acid  and  hydriodic  acid. 

|3  (.  O3       _|_       QTTT 

'       :=:      TTS   r  V       -r      oJtll 


Phosphorus  3  molecules  Phosphorous 

triiodide.  of  water.  acid. 

Amorphous  phosphorus  in  powder  is  introduced  into  a  glass- 
stoppered  retort  the  neck  of  which  is  soldered  to  the  delivery- 
tube  (Fig.  49),  and  covered  with  a  layer  of  water ;  the  iodine 
is  then  added,  and  on  the  application  of  a  gentle  heat  a  regular 
current  of  hydriodic  acid  is  obtained.  The  gas  may  be  col- 
lected, like  chlorine,  by  downward  displacement  in  dry  jars. 

Properties. — Hydriodic  acid  is  a  colorless  gas  producing 
white  fumes  in  the  air.  It  may  be  condensed  to  a  yellow 
liquid  by  strong  pressure  or  intense  cold,  and  can  even  be  solid- 
ified. Dry  oxygen  decomposes  it  at  a  high  temperature,  water 
being  formed  and  the  iodine  being  set  at  liberty. 

If  a  lighted  taper  be  applied  to  a  mixture  of  hydriodic  acid 
and  oxygen,  the  violet  vapor  of  the  iodine  set  free  is  instantly 
apparent. 

This  decomposition  of  hydriodic  acid  by  oxygen  takes  place 
at  ordinary  temperatures  in  the  presence  of  water.  A  solution 


HYDRIODIC   ACID.  133 

of  hydriodic  acid  exposed  to  the  air  rapidly  becomes  brown, 
and  after  a  time  deposits  crystals  of  iodine. 

Solution  of  hydriodic  acid  is  prepared  by  passing  the  gas  into 
water  cooled  to  0°.     It  may  also  be  made  by  passing  a  current 
of  hydrogen  sulphide  through  water  holding  iodine  in  suspen- 
sion ;  hydriodic  acid  is  formed,  and  sulphur  is  precipitated. 
H2S  -f  F  =  2HI  -f  S 

The  saturated  solution  of  hydriodic  acid  has  a  density  of 
1.7,  and  fumes  in  the  air.     When  freshly  prepared,  it  is  color- 


FIG.  49. 

less ;  when  heated,  it  loses  part  of  its  gas,  and  finally  distils 
unaltered  at  126°.  The  saturated  solution  contains  57.7  per 
cent,  of  the  dry  acid. 

Chlorine  and  bromine  at  once  decompose  hydriodic  acid, 
combining  with  the  hydrogen  and  setting  free  the  iodine.  The 
experiment  may  be  made  by  pouring  a  few  drops  of  bromine 
into  a  jar  filled  with  hydriodic  acid  gas,  when  the  appearance 
of  a  violet  vapor  immediately  indicates  the  liberation  of  iodine. 

Potassium,  zinc,  iron,  mercury,  and  silver  decompose  hydri- 
odic acid,  but  with  unequal  energies,  setting  free  the  hydrogen. 

12 


134  ELEMENTS   OP   MODERN   CHEMISTRY. 

Sulphuric  acid  also  decomposes  it,  and  is  itself  reduced  to  sul 
phurous  oxide. 

H2SO  +  2HI  =  2H20  -f  SO2  -f  I2 
Nitric  acid  is  still  more  readily  reduced  by  hydriodic  acid. 
2HN03     +    2HI    =    2H20     +        2N02        -f    P 

Nitric  acid.  Nitrogen  peroxide. 

IODINE   OXIDES   AND   OXYGEN  ACIDS. 

Among  the  compounds  of  iodine  and  oxygen,  iodic  and  peri- 
odic oxides  are  the  only  ones  known  with  certainty.  The  ex- 
istence of  the  other  oxides,  although  possible  and  even  probable, 
has  not  been  fully  demonstrated.  These  compounds  would  form 
the  following  series : 

Hypoiodous  oxide IZQ 

lodous  oxide I203 

Iodine  peroxide *     ...  120* 

Iodic  oxide I2Q5 

Periodic  oxide PQ7 

In  combining  with  water,  these  oxides  form  acids ;  it  is  only 
necessary  to  describe  here  iodic  and  periodic  acids. 
TO5  -f  H2O  ==  2HI03,2  molecules  iodic  acid. 
PO7  +  H20  ==  2HI04,2  molecules  periodic  acid, 

IODIC   ACID. 
HIO»  ==  I02(OH) 

Iodic  acid  is  formed  when  iodine  is  submitted  to  the  action 
of  energetic  oxidizing  agents,  such  as  concentrated  nitric  acid 
or  a  mixture  of  nitric  acid  and  potassium'  chlorate.  It  is  also 
formed  by  the  action  of  an  excess  of  chlorine  on  iodine  in 
presence  of  water. 

p  +  5CP  -|-  6H20  ==  10HC1  -f  2HI03 
Preparation. — Iodic  acid  may  be  conveniently  prepared  by 
heating  iodine  and  potassium  chlorate  with  dilute  nitric  acid. 
The  oxygen  of  the  chlorate  oxidizes  the  iodine  to  iodic  acid, 
and  on  adding  barium  nitrate  to  the  liquid,  barium  iodate  is 
precipitated.  The  latter  salt  is  decomposed  by  sulphuric  acid ; 
iodic  acid  is  set  free  in  the  solution,  and  barium  sulphate  is 
precipitated ;  the  filtered  solution  is  concentrated  by  evapora- 
tion in  vacuo. 

Properties. — Iodic  acid  is  solid,  and  crystallizes  in  hex- 
agonal tables.  When  heated  to  170°  it  loses  water  and  is 


PERIODIC   ACID.  135 

converted  into   iodic  oxide,  and   at  a  red  heat  the  latter  is 
decomposed  into  iodine  and  oxygen. 

It  is  seen  that  iodic  acid  is  much  more  stable  than  its  ana- 
logue, chloric  acid  ;  nevertheless  it  is  easily  reduced  by  bodies 
avid  of  oxygen. 

If  sulphurous  acid  be  added  to  a  solution  of  iodic  acid,  a 
precipitate  of  iodine  is  formed  instantly,  but  an  excess  of  sul- 
phurous acid  redissolves  the  precipitate,  part  of  the  water  being 
decomposed  and  hydriodic  and  sulphuric  acids  being  formed. 

Iodic  acid  is  also  decomposed  by  hydriodic  acid.     If  a  solu- 
tion of  iodic  acid  be  poured  into  a  solution  of  starch,  no  color- 
ation   appears,   but  the    characteristic  blue   color  is  at  once 
developed  on  adding  a  drop  of  hydriodic  acid. 
HIO3  +  5HI  =  3H20  +  3P 

PERIODIC   ACID. 

This  acid  has  been  obtained  from  disodic  periodate,  a  salt 
which  is  precipitated  when  a  current  of  chlorine  is  passed 
through  a  solution  of  sodium  iodate  mixed  with  sodium  hydrate. 

NalO3  +  3NaOH  +  CP  =  I05  j^Vo  +  2NaCl 

Sodium  iodate.    Sodium  hydrate.  Disodic  periodate.      Sodium  chloride. 

The  crystalline  precipitate  is  dissolved  in  nitric  acid,  and 
lead  nitrate  is  added  to  the  solution  ;  lead  periodate  is  precipi- 
tated, and  this  salt  is  exactly  decomposed  by  sulphuric  acid  ; 
the  liquid  is  filtered  to  separate  the  lead  sulphate,  and  evapo- 
rated at  a  gentle  heat.  The  periodic  acid  crystallizes  out  in 
colorless,  deliquescent,  rhombic  prisms,  fusible  at  130°.  These 
crystals  contain  H3I05  -f  H20.  At  160°  they  lose  water  and 
are  converted  into  a  white  mass  of  periodic  oxide. 
2(H3I05.H20)  =  POT  +  5H20 

Between  180  and  190°  periodic  oxide  abandons  oxygen,  and 
is  converted  into  iodic  oxide,  I205. 

Periodic  acid  forms  several  varieties  of  salts. 


There    is    a    diargentic     periodate,    I05  j    jj^,H20     = 
~t~  H2()'  corresP°nding  to  the  disodic  salt  before 


mentioned;  but  there  is  also  a  silver  periodate,  AglO4,  to 
which  corresponds  an  acid,  HIO*,  having  a  composition  analo- 
gous to  that  of  perchloric  acid,  but  which  has  not  yet  been 
obtained. 


136  ELEMENTS   OP   MODERN   CHEMISTRY. 

Analogy  between  Chlorine,  Bromine,  and  Iodine. — Chlo- 
rine, bromine,  and  iodine  present  a  striking  analogy  in  their 
chemical  properties,  and  this  analogy  is  seen  in  all  of  their 
compounds.  They  combine  with  hydrogen,  atom  for  atom, 
forming  the  acids 

HC1 
HBr 
HI 

and  it  is  seen  that  the  atoms  of  chlorine,  bromine,  and  iodine 
are  equivalent  to  each  other  and  to  an  atom  of  hydrogen  ;  each 
of  these  elements  is  monatomic. 

Their  affinities  for  hydrogen  are  far  from  being  equal ;  in  this 
respect  chlorine  is  more  powerful  than  bromine,  and  bromine 
than  iodine.  The  contrary  has  been  noticed  regarding  their 
affinities  for  oxygen,  for  the  oxygen  acids  of  iodine  are  more 
stable  than  those  of  chlorine. 

The  analogy  between  these  three  elements  is  followed  out 
in  the  constitution  of  their  oxides  and  acids,  and  in  their  com- 
binations with  the  metals.  The  chlorides,  iodides,  and  bro- 
mides possess  in  general  the  same  constitution,  and  it  is  to  be 
remarked  that  the  greater  part  of  these  binary  compounds  are 
soluble  in  water  and  are  crystallizable  like  salts,  of  which  they 
otherwise  present  the  characters.  Hence  the  name  halogen 
bodies,  which  was  applied  by  Berzelius  to  this  group  of  elements, 
to  indicate  that  they  form  salts  in  combining  with  the  metals. 


FLUORINE. 

Fl  =  19. 

This  is  a  body  belonging  to  the  same  group  just  considered, 
and  having  a  chemical  energy  much  superior  to  that  of  chlorine. 
It  exists  in  the  common  mineral  fluor  spar,  which  is  a  combina- 
tion of  fluorine  and  calcium.  But  fluorine  has  never  been 
isolated ;  it  attacks  all  vessels,  and  it  would  be  necessary  to 
have  apparatus  and  vessels  cut  from  fluor  spar  in  order  to  con- 
tain it.  There  is  a  compound  of  fluorine  and  hydrogen. 

HYDROFLUORIC   ACID. 

Molecular  weight  HF1 =20 

This  compound  is  prepared  by  decomposing  powdered  cal- 
cium fluoride  with  sulphuric  acid. 

CaFP     +     H'SO*     =     CaSO*     +     2HF1 

Calcium  fluoride.  Calcium  sulphate. 


HYDROFLUORIC   ACID. 


137 


The  operation  is  conducted  in  a  leaden  retort,  to  which  is 
adapted  a  receiver  of  the  same  metal  surrounded  by  a  freezing 
mixture   (Fig.   50). 
The        hydrofluoric 
acid    condenses     as 
a   very  acid  liquid, 
which  fumes  strong- 
ly in   the  air.     Its 
density  is  LOG.     In 
this  state  it  still  re- 
tains    water ;      but 
Fremy   obtained    it  ^f 
anhydrous    by    de-  Ig 
composing  dry   hy- 
drofluoride  of  fluor- 
ide    of    potassium,  Jb'io.  50. 
KF1,HF1,   by   heat 

in  a  platinum  retort.  This  salt  breaks  up  into  potassium  fluor- 
ide, which  remains,  and  hydrofluoric  acid,  which  is  disengaged 
and  must  be  condensed  in  a  platinum  receiver  cooled  to  — 20°. 
Pure  and  anhydrous  hydrofluoric  acid  is  liquid  at  ordinary  tem- 
peratures ;  it  is  very  mobile,  and  boils  at  19.4°  (Gore).  It  is 
extremely  corrosive,  and  manipulations  with  it  should  be  con- 
ducted with  great  care.  Its  affinity  for  water  is  so  great  that 
each  drop  of  the  acid  let  fall  into  that  liquid  produces  a  hissing 
noise,  as  would  a  red-hot  iron.  The  solution  is  employed  for 
etching  upon  glass,  for  hydrofluoric  acid  attacks  and  corrodes 
that  substance.  This  effect  is  due  to  the  action  of  the  acid 
upon  the  silica  of  the  glass,  which  it  converts  into  either  sili- 
con fluoride  or  hydrofluosilicic  acid,  as  will  be  seen  farther  on. 


FIG.  51. 

A  design  may  readily  be  engraved  on  glass  by  covering  the 
glass  with  a  thin  coating  of  wax,  through  which  the  design  is 

12* 


138 


ELEMENTS   OF    MODERN   CHEMISTRY. 


traced  with  a  sharp  point ;  the  glass  is  then  placed  over  a  leaden 
capsule  containing  a  mixture  of  powdered  calcium  fluoride,  and 
sulphuric  acid  (Fig.  51),  which  is  gently  heated  by  a  spirit-lamp. 
Hydrofluoric  acid  vapor  is  disengaged  and  attacks  the  glass 
wherever  it  is  not  protected  by  the  wax.  When  the  wax  is  re- 
moved, the  design  is  found  to  be  permanently  etched  on  the  glass. 
A  dilute  solution  of  hydrofluoric  acid  or  a  bath  of  hydro- 
fluoride  of  potassium  fluoride  may  be  employed  instead  of  the 
vapor  in  the  former  experiment,  but  in  this  case  the  etched 
portions  are  transparent  and  not  opaque  as  when  produced  by 
the  vapor ;  they  may  be  rendered  opaque  by  adding  a  salt,  such 
as  potassium  or  ammonium  sulphate,  to  the  bath. 


NITROGEN. 

Density  compared  to  air 0.9714 

Density  compared  to  hydrogen 14.1 

Atomic  weight  N =  14. 

Nitrogen  is  one  of  the  elements  of  the  air,  and  it  was  from 
air  that  it  was  first  obtained  in  a  pure  state  by  Lavoisier  and 
Scheele,  in  1777.  To  obtain  nitrogen  from  the  atmosphere  it 
is  only  necessary  to  remove  the  other  element,  oxygen. 

Preparation. — A  flat  piece  of  cork,  B  (Fig.  52),  floating  in 
the  pneumatic-trough,  supports  a  small  capsule  containing  a 

fragment  of  phos- 
phorus. The  latter 
is  inflamed,  and  the 
capsule  immediately 
covered  with  a  bell- 
jar.  The  heat  pro- 
duced by  the  com- 
bustion at  first  ex- 
pands the  air  and 
drives  out  a  portion, 
but  in  a  few  minutes 

the  water   rises  in 

-riE    the  jar,  taking  the 
place  of  the  oxygen 

FIG.  52.  which  has  been  con- 

sumed.    When  the 

phosphorus  is  extinguished,  the  experiment  has  terminated. 
The  water  gradually  dissolves  the  white  smoke  of  phosphoric 
oxide  which  fills  the  jar,  and  there  remains  a  colorless,  irre- 


AMMONIA.  139 

spirable  gas  that  will  not  support  combustion.     This  gas  is 
nitrogen,  still  mixed  with  traces  of  oxygen  and  carbonic  acid  gas. 

Pure  nitrogen  may  be  obtained  by  passing  a  current  of  air, 
previously  freed  from  moisture  and  carbon  dioxide,  through  a 
porcelain  tube  containing  incandescent  copper.  The  copper 
absorbs  the  oxygen,  and  pure  nitrogen  passes  out  at  the  end 
of  the  tube  and  may  be  collected  over  the  pneumatic  trough. 

Pure  nitrogen  may  also  be  obtained  by  heating  ammonium 
nitrite  in  a  glass  retort ;  heat  decomposes  this  salt  into  nitrogen 
and  water. 

(NH4)N02    =     2H20     -f     N2 

Ammonium  nitrite. 

Properties. — Nitrogen  is  a  colorless  gas,  somewhat  lighter 
than  the  air.  A  litre  of  this  gas  weighs  1.257  grammes.  It 
extinguishes  burning  bodies,  and  is  not  combustible  itself;  it 
produces  no  precipitate  in  lime-water.  Water  dissolves  only 
•fa  of  its  volume  of  nitrogen  at  0°.  Animals  are  quickly  suffo- 
cated in  an  atmosphere  of  pure  nitrogen,  but  the  gas  does  not 
exert  a  poisonous  influence  upon  the  economy. 

The  affinities  of  nitrogen  are  not  energetic.  It  combines 
directly  with  only  a  very  small  number  of  elements,  among 
which  may  be  mentioned  carbon,  silicon,  boron,  arid  titanium. 

Under  the  influence  of  a  series  of  electric  discharges  it  will 
unite  with  oxygen,  forming  nitrogen  peroxide  ;  with  hydrogen, 
forming  ammonia. 

AMMONIA. 

Density  compared  to  air 0.596 

Density  compared  to  hydrogen 8.60 

Molecular  weight  NH3 =  17. 

Ammonia  was  discovered  by  Priestley,  studied  by  Scheele, 
and  analyzed  by  Bertholet  in  1785. 

Preparation. — Equal  weights  of  quick-lime  and  sal  am- 
moniac, both  in  powder,  are  rapidly  mixed  in  a  mortar,  and 
the  mixture  introduced  into  a  glass  flask,  which  is  then  filled 
up  with  fragments  of  quick-lime.  A  cork  and  delivery-tube 
are  adapted  to  the  flask,  which  is  then  gently  heated  and  the 
gas  disengaged  collected  over  mercury. 

The  calcium  oxide  or  lime  decomposes  the  ammonium 
chloride  (sal  ammoniac),  with  the  formation  of  calcium 
chloride,  ammonia  gas,  and  water ;  the  latter  is  absorbed  by 
the  fragments  of  lime  which  fill  up  the  flask. 

2NH4C1     +        CaO   ==   2NH3     -f     CaCP  -f  H20 

Ammonium  chloride.    Calcium  oxide.    Ammonia.        Calcium  chloride. 


140  ELEMENTS   OF    MODERN    CHEMISTRY. 

A  solution  of  ammonia  in  water  may  be  prepared  by  passing 
the  gas  through  a  series  of  Wolff's  bottles,  about  half  filled  with 
water,  excepting  the  first,  which  should  only  contain  a  small 
quantity  destined  to  wash  the  gas. 

Physical  Properties. — Ammonia  is  a  colorless  gas,  having 
a  powerful  and  pungent  odor,  which  excites  tears.  Its  taste  is 
burning  and  caustic.  It  may  be  liquefied  by  a  temperature  of 
— 40°,  or  at  10°  under  a  pressure  of  6£  atmospheres.  Fara- 
day's method  of  liquefying  it  is  as  follows  :  ammonia  is  passed 
over  dry  silver  chloride,  by  which  it  is  absorbed.  The  silver 
chloride,  saturated  with  ammonia,  is  introduced  into  a  bent 
tube  (Fig.  53),  the  empty  limb  of  which  is  then  sealed  at  the 


FIG.  53.  Fio.54. 


blow-pipe.  The  end  containing  the  chloride  is  now  heated  in 
a  water-bath,  while  the  empty  end  is  cooled  in  a  freezing  mix- 
ture (Fig.  54).  The  ammonia  is  driven  out  from  the  silver 
chloride,  and  condenses  into  a  transparent  liquid  in  the  cooler 
branch.  Faraday  succeeded  in  solidifying  ammonia  by  subject- 
ing this  liquid  to  rapid  evaporation.  In  the  solid  state  it  is  a 
white,  crystalline,  transparent  substance,  fusible  at  — 75°,  and 
having  only  a  feeble  odor.  According  to  Bunsen,  liquid  ammo- 
nia boils  at  — 35°  under  a  pressure  of  0.7493  metre  ;  its  density 
is  0.76. 

Ammonia  gas  is  very  soluble  in  water,  which  dissolves  1000 
times  its  volume  at  0°,  and  about  740  times  its  volume  at 
15°.  The  rapid  absorption  of  ammonia  by  water  may  be  strik- 
ingly shown  by  the  following  experiment.  A  bottle,  A  (Fig.  55), 
is  filled  with  ammonia  gas,  and  fitted  with  a  cork,  through 
which  passes  a  tube  drawn  out  at  both  extremities,  and  the 
outer  end  of  which  is  sealed.  If  this  end  be  plunged  under 
water  and  the  point  be  broken  off,  the  water  at  once  rises  into 


AMMONIA. 


141 


the  bottle,  forming  a  fountain,  and  the  vessel  becomes  filled 
with  water  in  a  very  short  time. 

The  aqueous  solution  of  ammonia  possesses  the  odor  of  the 
gas ;  it  is  caustic,  and 
was  formerly  called  vol- 
atile alkali  and  spirits 
of  hartshorn.  It  is 
largely  used  in  the  arts 
and  as  a  reagent.  Its 
density  is  0.855.  When 
heated,  it  loses  ammonia 
gas,  the  whole  of  which 
may  be  driven  out  by 
boiling. 

Composition  of  Am- 
monia,— 200  volumes 
of  ammonia  gas  are  in- 
troduced into  an  eudi- 
ometer, and  electric 
sparks  are  passed 
through  the  gas  for 
some  time  by  means  of 
a  Ruhmkorff  coil  (Fig. 
56).  When  the  experiment  has  terminated,  the  volume  of 
gas  will  be  found  to  have  doubled.  200  volumes  of  oxygen 
are  added  to  the  400  volumes  of  gas  thus  obtained,  and  a  spark 
is  passed;  an  explosion  takes  place,  and  after  making  the 


Fio.  55. 


FJG.  56. 


necessary  corrections  for  temperature  and  pressure,  the  600 
volumes  of  gas  are  found  to  be  reduced  to  150  volumes ;  450 
volumes  have  thus  disappeared  to  form  water. 


142 


ELEMENTS   OP   MODERN   CHEMISTRY. 


These  450  volumes  must  have  contained 

300  volumes  of  hydrogen, 
150  volumes  of  oxygen. 

Consequently  the  200  volumes  of  ammonia  gas,  which  were 
decomposed  by  the  spark  into  400  volumes,  must  have  been 
formed  by  the  union  of 

300  volumes  of  hydrogen, 
100  volumes  of  nitrogen. 

The  latter  gas  remains  in  the  eudiometer,  together  with  the 
50  volumes  of  oxygen  that  were  employed  in  excess. 

From  this  analysis  it  is  seen  that  two  volumes  of  ammonia 
contain  three  volumes  of  hydrogen  and  one  volume  of  nitrogen, 
a  composition  which  is  expressed  by  the  formula  NH3. 

Chemical  Properties. — Ammonia  gas  is  decomposed  by  a 
high  temperature,  as  by  a  series  of  electric  sparks.  The  experi- 
ment may  be  made  by  passing  the  gas  through  a  porcelain  tube 


FIG.  57. 

filled  with  fragments  of  broken  porcelain  and  heated  to  white- 
ness, and  collecting  the  gas  resulting  from  the  decomposition  in 
vessels  filled  with  water  (Fig.  57).  This  gas  is  found  to  be  a 
mixture  of  three  volumes  of  hydrogen  and  one  volume  of 
nitrogen. 

The  decomposition  takes  place  more  readily  if  iron,  copper, 
or  platinum  wires  be  introduced  into  the  porcelain  tube. 


AMMONIA. 


143 


latter  metal  is  not  altered,  but  the  iron  and  copper  become 
brittle  and  retain  a  few  per  cent,  of  nitrogen.  The  decompo- 
sition of  the  ammonia  seems  here  to  be  favored  by  the  forma- 
tion of  metallic  nitrides,  unstable  compounds  which  are  almost 
entirely  decomposed  by  the  prolonged  action  of  the  heat. 

Ammonia  gas  will  not  burn  in  the  air,  but  a  mixture  of  four 
volumes  of  ammonia  and  three  volumes  of  oxygen  will  explode 
on  the  application  of  a  flame. 

2NH3  +  O3  =  3H20  +  N2 

Ammonia  will  burn  in  an  atmosphere  of  oxygen.  A  jet  of 
ammonia  escaping 
through  a  tube  drawn 
out  to  a  point  may  be 
ignited  on  the  instant 
that  it  is  plunged  into 
a  jar  of  oxygen,  and 
will  continue  to  burn 
with  a  yellowish  flame 
until  the  oxygen  is 
consumed  (Fig.  58). 

Independently  of 
this  rapid  combus- 
tion, ammonia  may 
undergo  a  slow  com- 
bustion under  the  fol- 
lowing conditions : 

The  vessel  A  (Fig.  59)  contains  a  solution  of  ammonia, 
above  which  is  suspended  a  spiral  of  platinum  wire.  The  solu- 
tion is  gently  heated,  and  a  rapid  current  of  oxygen  gas  is 
forced  through  it.  The  mixed  ammonia  and  oxygen  gases 
come  in  contact  with  the  platinum  spiral  and  combine  together, 
their  union  developing  so  much  heat  that  the  spiral  is  heated 
to  redness.  The  vessel  sometimes  becomes  filled  with  white 
fumes  of  ammonium  nitrite.  The  nitrous  acid  is  produced  by 
the  slow  oxidation  of  the  ammonia.  If  a  mixture  of  oxygen 
and  ammonia  gases  be  passed  through  a  heated  tube  contain- 
ing spongy  platinum,  nitric  acid  and  water  will  be  formed 
and  disengaged  in  vapor. 

Action  of  Chlorine  and  Iodine  upon  Ammonia. — Chlorine 
instantly  decomposes  ammonia,  combining  with  its  hydrogen. 
If  a  drawn-out  tube  through  which  a  jet  of  ammonia  is  escaping 


FIG.  58. 


144 


ELEMENTS   OF    MODERN    CHEMISTRY. 


be  plunged  into  a  bottle  filled  with  dry  chlorine  (Fig.  60),  the 
ammonia  takes  fire  immediately,  and  white  vapors  of  ammo- 
nium chloride  are  formed. 

4NH3  -f  CP  ==  3NH4C1  -f  N 

If  a  long  tube  closed  at  one  end  be  almost  entirely  filled 
with  saturated  chlorine  water  and  then  filled  up  with  a  solu- 
tion of  ammonia,  and  quick|y 
inverted  on  the  pneumatic 
trough,  the  lighter  solution  of 
ammonia  will  rise  through  the 
chlorine-water  and  will  be  de- 
composed according  to  the  pre- 
ceding equation.  Ammonium 
chloride  will  remain  in  solution, 
while  the  nitrogen  will  collect 
at  the  top  of  the  tube. 

Nitrogen  Chloride. — Under 
other  conditions  the  nitrogen 
may  combine  with  the  chlorine, 
forming  a  very  explosive  and 
dangerous  compound,  nitrogen 
chloride. 

This  experiment  may  be  made 
as  follows  :  A  small  jar  of  chlo- 
rine is  inverted  in  a  saucer  con- 
taining a  solution  of  ammonium  chloride.  The  ammonia  of 
this  salt  is  slowly  decomposed  by  the  chlorine,  with  the  for- 
mation of  hydrochloric  acid  and 
nitrogen  chloride. 

As  the  chlorine  is  absorbed,  the 
level  of  the  liquid  in  the  jar  rises 
and  a  drop  of  a  yellow  liquid  soon 
collects  on  the  surface.  A  light  tap 
on  the  vessel  causes  it  to  sink  through 
the  solution  into  the  saucer.  This 
oily  body  is  nitrogen  chloride.  The 
jar  may  now  be  removed  and  a  small 
piece  of  phosphorus  thrown  into  the 
saucer,  and  pushed  from  a  distance 
towards  the  drop  of  nitrogen  chloride 
by  the  aid  of  a  long  wooden  rod. 


FIG.  59. 


FIG.  60. 


AMMONIA.  145 

As  soon  as  the  two  substances  come  into  contact,  the  nitrogen 
chloride  explodes  and  the  saucer  is  broken  into  pieces. 

The  formula  NCF  has  been  attributed  to  this  body. 

Nitrogen  Iodide.  —  There  is  another  explosive  compound 
analogous  to  nitrogen  chloride,  but  containing  iodine.  It  is 
obtained  as  a  black  powder  by  treating  powdered  iodine  with 
ammonia;  when  dry  it  explodes  with  great  violence  on  the 
lightest  touch,  and  sometimes  spontaneously.  Bunsen  has 
attributed  to  it  the  formula  N2HT. 

According  to  Stahlschmidt,  the  composition  of  nitrogen 
iodide  corresponds  to  the  formula  NF,  when  this  body  is  pre 
pared  by  the  action  of  an  alcoholic  solution  of  iodine  upon 
aqueous  ammonia  ;  but  if  both  bodies  be  in  alcoholic  solution, 
an  iodide  is  obtained  having  the  formula  NHP. 

If  this  be  correct,  these  bodies  present  very  simple  relations 
with  ammonia. 

ci  ri  ri 

K-.i  Nil 


N    H  N    Cl  -. 

(H  (ci  (i  (H 

Ammonia.  Nitrogen  chloride.      Triiodammonia.      Diiodammonia. 

Trichlorammonia.  Nitrogen  iodides. 

The  substitution  of  the  chlorine  or  iodine  for  hydrogen  takes 
place  atom  for  atom. 

Action  of  Potassium  upon  Ammonia.  —  When  potassium 
is  heated  in  an  atmosphere  of  ammonia,  the  brilliant  surface 
of  the  metal  becomes  covered  with  a  greenish-black  liquid, 
and  at  the  same  time  hydrogen  is  disengaged.  The  metal 
entirely  disappears  little  by  little,  and,  on  cooling,  the  liquid 
solidifies  to  an  olive-green  mass.  This  substance  represents 
ammonia  in  which  one  atom  of  hydrogen  has  been  replaced 
by  an  atom  of  potassium. 

H)  K) 

H  V  N  =  Ammonia.  H  }-  N  =  Potassium  amide. 

HJ  HJ 

When  it  is  treated  with  water,  ammonia  is  regenerated  and 
potassium  hydrate  is  formed. 

KNH2     +     H20    ==    KOH     +     NH3 

Potassium  amide.  Potassium  hydrate'. 

Ammonium  Amalgam.  —  If  liquid  amalgam  of  potassium 

or  sodium  and  mercury  be  treated  with  a  saturated  solution  of 

ammonium  chloride,  the  amalgam  increases  in  volume,  assumes 

a  buttery  consistence,  and  is  converted  into  a  soft,  light  mass 

G  13 


146  ELEMENTS    OF   MODERN    CHEMISTRY. 

having  the  metallic  lustre  of  mercury.  It  will  retain  the 
impression  of  the  finger  and  will  float  upon  water;  but  it 
gradually  decomposes,  losing  hydrogen  and  ammonia,  and  only 
mercury  remains.  This  unstable  body  is  called  ammonium 
amalgam.  In  it  the  mercury  is  combined  with  a  group,  NH4, 
which  contains  all  of  the  hydrogen  of  the  ammonium  chloride, 
the  chlorine  of  which  has  combined  with  the  potassium. 
NH:!.HC1  —  Cl  =  NH* 

Ammonium  chloride.  Radical  ammonium. 

It  has  recently  been  found  that  the  ammonium  amalgam  is 
very  compressible,  and  that  its  diminution  in  volume  under 
pressure  sensibly  follows  Mariotte's  law.  It  has  hence  been 
concluded  that  the  ammonium  does  not  exist  in  combination 
with  the  mercury,  and  that  the  increased  volume  of  the  latter 
is  due  simply  to  an  absorption  of  gas.  It  is  difficult  to  admit 
this,  for  the  compressibility  of  the  ammonium  amalgam  proves 
only  that  the  compound  has  no  stability,  and  begins  to  decom- 
pose almost  immediately  on  its  formation.  The  disengaged 
gases,  which  are  in  the  exact  proportion  NH3  -f-  H,  may  be 
retained  by  the  pasty  amalgam  remaining :  they  could  not  be 
absorbed  by  the  liquid  mercury. 

Ammonium  Theory. — The  reaction  which  has  just  been 
described  is  of  great  importance,  and  directly  supports  the 
ammonium  theory  suggested  by  Ampere.  According  to  this 
theory,  the  ammoniacal  salts  are  analogous  in  constitution  to 
ordinary  salts,  from  which  they  differ  only  by  the  substitution 
of  a  compound  radical,  ammonium,  for  a  simple  radical.  The 
following  formulae  explain  this  proposition  : 

NH3.HC1         =    (NH*)C1       analogous  to     KC1 

Ammonium  chloride.  Potassium  chloride. 

NH3.HN03      =    (NH4)N03  analogous  to     KNO3 

Ammonium  nitrate.  Potassium  nitrate. 


NH3.H2S          =         g     S     analogous  to  S 

Ammonium  sulphydrate.  Potassium  sulphydrate. 

(NH3)2.H2S  ^  |  S    analogous  to     |  j  S 


Ammonium  sulphide.  Potassium  sulphide. 

AMMONIUM   CHLORIDE. 

NH*C1 

This  salt  was  formerly  obtained  from  Egypt,  where  it  was 
made  by  subliming  the  soot  produced  by  the  combustion  of 


AMMONIUM  SULPHYDRATE  AND  AMMONIUM  SULPHIDE.  147 

camel's  dung.  It  is  now  prepared  in  large  quantities  from  gas- 
liquor,  or  the  water  condensed  in  the  manufacture  and  purifi- 
cation of  illuminating  gas  from  coal.  This  liquor  is  heated 
with  lime,  ammonia  is  disengaged  and  is  conducted  into  hydro- 
chloric acid.  Ammonium  chloride  is  obtained  by  simply 
evaporating  the  solution.  It  is  purified  by  sublimation  in 
stoneware  pots  which  are  heated  in  a  furnace  out  of  which  the 
upper  parts  of  the  pots  project.  There  the  volatilized  chloride 
condenses,  and  the  sublimed  product  is  known  in  commerce  as 
sal  ammoniac,  or  muriate  of  ammonia. 

It  generally  occurs  as  white  or  grayish,  compact  masses, 
having  a  crystalline  fibrous  structure.  Its  taste  is  sharp  and 
salty.  It  dissolves  in  two  and  a  half  parts  of  cold,  and  in  its 
own  weight  of  boiling  water.  It  is  deposited  from  a  satu- 
rated solution  in  small  octahedra,  grouped  together  in  needles, 
and  presenting  a  fern-leaf-like  appearance.  At  a  high  tem- 
perature it  volatilizes  without  melting  and  sublimes  without 
decomposition. 

Ammonium  chloride  is  formed  by  the  union  of  equal  vol- 
umes of  hydrochloric  acid  and  ammonia  gases. 

AMMONIUM     SULPHYDRATE     AND     AMMONIUM 
SULPHIDE. 

Hydrogen  sulphide  and  ammonia  gases  unite  in  the  cold 
in  two  different  proportions,  forming  two  compounds,  ammo- 
nium sulphydrate  and  ammonium  sulphide. 

H2S        -f        NH3 

Hyrogen  sulphide.  Ammonia.  Ammonium  sulphydrate. 

(2  vol.)  (2  vol.) 

IPS        -f        2NH3 

Hydrogen  sulphide.  Ammonia.  Ammonium  sulphide. 

(2  vol.)  (4  vol.) 

These  compounds  are  definite,  but  are  decomposed  into  their 
elements  by  heat.  Horstmann  and  Salet  have  shown  that  hy- 
drogen sulphide  and  ammonia  gases  may  be  mixed  in  all  pro- 
portions without  contraction  in  volume  taking  place,  provided 
the  temperature  be  maintained  above  60°. 

Ammonium  sulphydrate  is  generally  obtained  in  solution  by 
saturating  aqueous  ammonia  with  hydrogen  sulphide.  This 
solution  is  colorless,  but  acquires  a  yellow  color  on  exposure  to 


148  ELEMENTS    OP    MODERN    CHEMISTRY. 

the  air.  When  a  quantity  of  ammonia  is  added  to  it  equal  to 
that  which  it  already  contains,  ammonium  sulphide,  (NH*/S, 
is  formed,  which  corresponds  to  potassium  sulphide,  K2S. 

Ammonium  sulphide  is  largely  employed  in  the  laboratory 
as  a  reagent  for  the  detection  of  certain  metals. 

If  ammonium  sulphide  be  added  to  a  solution  of  ferrous 
sulphate,  a  double  decomposition  takes  place ;  ammonium  sul- 
phate is  formed  and  remains  in  solution,  while  ferrous  sulphide 
forms  a  black  precipitate. 

FeSO       +     (NH*)2S     =       FeS       -f     (NH*)2SO 

Ferrous  sulphate.  Ferrous  sulphide.      Ammonium  sulphate. 

The  salts  of  zinc,  manganese,  cobalt,  and  nickel  are  likewise 
precipitated  as  sulphides  by  ammonium  sulphide. 

The  salts  of  aluminium  and  chromium  are  precipitated  as 
hydrates,  hydrogen  sulphide  being  disengaged. 

The  preceding  salts  are  not  precipitated  by  hydrogen  sul- 
phide (the  zinc  salts  are  not  precipitated  if  they  be  acid),  but 
the  latter  reagent  precipitates  in  the  form  of  sulphides  the  salts 
of  lead,  bismuth,  copper,  cadmium,  mercury,  silver,  antimony, 
tin,  gold,  and  platinum.  The  sulphides  of  the  latter  four 
metals  dissolve  in  an  excess  of  ammonium  sulphide. 

The  sulphides  of  arsenic,  tin,  antimony,  gold,  and  platinum 
all  form  compounds  with  ammonium  sulphide,  in  which  the 
latter  plays  the  part  of  a  base. 

AMMONIUM   NITRATE. 

(NH«)NO* 

Ammonium  nitrate  is  prepared  by  saturating  nitric  acid 
with  ammonia.  It  crystallizes  in  large,  transparent,  fusible 
prisms,  which  are  very  soluble  in  water  and  produce  a  notable 
depression  of  temperature  in  the  act  of  solution,  extending 
even  to  — 15°.  At  300°  ammonium  nitrate  is  decomposed 
into  nitrogen  monoxide  and  water.  It  is  used  for  the  prepa- 
ration of  nitrogen  monoxide,  much  used  as  an  anaesthetic. 

AMMONIUM    CARBONATE. 

When  dry  carbon  dioxide  and  ammonia  gases  are  mixed  in 
the  proportion  of  2  volumes  of  the  first  to  4  volumes  of  the 
second,  they  condense,  forming  a  white  powder,  which  is  am- 


AMMONIUM    SULPHATE — HYDEOXYLAMINE.  149 

monium  carbamate,  a  compound  which  was  formerly  called 
anhydrous  carbonate  of  ammonia. 

CO2    -f-    2NH3    = 


Ammonium  carbamate. 

The  ammonium  carbonate  of  commerce  is  generally  consid- 
ered as  a  sesquicarbonate.  It  contains  2[C02(NH4)2]  +  CO2  + 
2H20.  It  is  obtained  by  heating  a  mixture  of  equal  parts  of 
ammonium  sulphate  and  chalk  in  a  subliming  apparatus. 
Ammonia  and  water  are  disengaged,  and  the  sesquicarbonate 
of  ammonium  sublimes. 

Recently  sublimed  ammonium  sesquicarbonate  is  transparent 
and  crystalline.  It  has  a  strong  ammoniacal  odor  and  a  sharp 
caustic  taste.  When  exposed  to  the  air  it  gradually  loses 
ammonia  and  is  converted  into  ammonium  acid  carbonate. 

Ammonium  Acid  Carbonate.  —  This  salt,  which  is  com- 
monly known  as  bicarbonate  of  ammonia,  may  be  obtained  by 
passing  a  current  of  carbonic  acid  gas  into  aqueous  ammonia, 
to  saturation.  The  acid  salt  is  deposited  in  right  rhombic 
prisms.  The  neutral  carbonate  of  ammonium  is  not  known. 
These  salts  present  the  following  relations  to  the  hypothetical 
carbonic  acid  : 


OH  OH  ONH< 

Carbonic  acid.  Ammonium  acid  Ammonium 

(Hypothetical.)  carbonate.  carbonate. 

AMMONIUM   SULPHATE. 

(NH<)2SO* 

This  salt  is  obtained  in  the  arts  by  passing  the  ammonia 
that  is  disengaged  when  gas-liquor  is  heated  with  lime  into 
dilute  sulphuric  acid.  It  crystallizes  in  right  rhombic  prisms. 

It  is  colorless  and  has  a  sharp  taste.  It  dissolves  in  two 
parts  of  cold,  and  in  its  own  weight  of  boiling,  water.  It  is 
insoluble  in  alcohol. 

HYDROXYLAMINE. 
NH*(OH) 

This  remarkable  compound  was  discovered  by  Lossen.  It 
is  formed  when  ethyl  nitrate  is  reduced  by  tin  and  hydrochlo- 
ric acid.  It  is  also  a  product  of  the  action  of  dilute  nitric  acid 
upon  tin,  and  that  of  hydrochloric  acid  and  tin  upon  ammo- 
nium nitrate. 

13* 


150  ELEMENTS   OF   MODERN   CHEMISTRY. 

Finally,  Lessen  has  prepared  it  synthetically  by  passing  a 
current  of  nitrogen  dioxide  over  tin  moistened  with  hydro- 
chloric acid,  which  determines  a  disengagement  of  hydrogen. 

2NO   +   3H2  =  2[NH'2(OH)] 

In  the  first  reactions  the  nitric  acid  is  reduced  by  the  hy- 
drogen resulting  from  the  action  of  a  dilute  acid  upon  tin,  and 
which  is  then,  just  as  it  is  set  free,  in  what  is  called  the  nascent 
state. 

HNO3  +  3H2  =  2H20  +  NH2.OH 

Nitric  acid. 

The  hydroxylamine  thus  formed  remains  in  the  liquid  com- 
bined with  an  excess  of  acid.  It  possesses  the  properties  of  an 
energetic  base.  It  forms  definite  salts  with  the  acids,  and  can 
be  regarded  as  ammonia,  in  which  the  group  OH  (hydroxyl) 
has  been  substituted  for  one  atom  of  hydrogen. 


N  1  H 


H  (OH 

N  •}  H 


Ammonia.  Hydroxylamine. 

Thus  far  it  has  not  been  isolated  ;  when  a  solution  of  potas- 
sium hydrate  is  added  to  a  concentrated  solution  of  a  salt  of 
hydroxylamine,  nitrogen  is  disengaged  and  ammonia  is  formed. 
3(NH2.OH)  =  N2  -f  NH3  -f  3H20 

Lossen  has  obtained  an  aqueous  solution  of  hydroxylamine 
by  decomposing  a  dilute  solution  of  hydroxylamine  sulphate 
with  the  exact  quantity  of  baryta-  water  sufficient  to  precipitate 
the  sulphuric  acid. 

Hydroxylamine  possesses  reducing  properties  ;  it  precipi- 
tates copper  and  mercury  in  the  metallic  state  from  solutions 
of  their  salts. 

OXYGEN   COMPOUNDS   OF  NITROGEN. 

Five  compounds  of  nitrogen  and  oxygen  are  known. 

ATOMIC 
COMPOSITION.  VOLUMETRIC    COMPOSITION. 

Nitrogen  monoxide,  or  nitrous 

oxide  ........  N20      2  vol.  N  and  1  v.  0  condensed  in  2  v. 

Nitrogen  dioxide  .....  NO        1  vol.  N  and  1  v.  0  =  2  v. 

Nitrogen  trioxide      ....  N203     2  vol.  N  and  3  v.  0  condensed  in  2  v. 

Nitrogen  tetroxide,  or  nitrogen 

peroxide  .......  N20*     2  vol.  N  and  4  v.  0  condensed  in  2  v. 

Nitrogen  pentoxide,  or  nitric 

anhydride     ......  N205     2  vol.  N  and  5  v.  0  condensed  in  2  v. 


NITROGEN    MONOXIDE. 


151 


Nitrogen  trioxide  and  nitrogen  pentoxide  combine  with 
water,  forming  nitrous  and  nitric  acids. 

N203       +       H20      ==      2HN02 

Nitrogen  trioxide.  Nitrous  acid. 

N205  _|_  JJ2Q  =  2HN03 

Nitrogen  pentoxide.  Nitric  acid. 

NITROGEN   MONOXIDE. 

Density  compared  to  air 1.527 

Density  compared  to  hydrogen 22. 

Molecular  weight  N2Q =  44. 

This  gas,  known  also  as  protoxide  of  nitrogen,  nitrous  oxide, 
and  laughing-gas,  was  discovered  by  Priestley  in  1776. 

Preparation. — It  is  obtained  by  gently  heating  ammonium 
nitrate  in  a  glass  retort.  The  salt  melts,  and  then  decomposes 


FIG.  61. 

with  effervescence  into  water  and  nitrogen  monoxide,  which 
may  be  collected  over  water  (Fig.  61). 

(NH*)N03  =  N20  +  2H20 

Properties. — Nitrogen  monoxide  is  colorless  and  odorless, 
but  possesses  a  sweetish  taste.  It  is  not  permanent,  and  may 
be  liquefied  by  strong  pressure.  It  is  liquefied  on  a  consider- 
able scale  at  present,  that  it  may  be  transported  in  small  bulk 
for  the  use  of  dentists.  For  this  purpose  it  is  compressed  in 
strong  iron  reservoirs. 

A  remarkable  experiment  can  be  performed  as  follows :  A 
quantity  of  liquid  nitrogen  monoxide  is  poured  into  a  test-tube 
fixed  by  a  cork  in  the  neck  of  a  bottle ;  a  portion  of  it 
instantly  volatilizes,  producing  intense  cold.  If  now  a  little 
mercury  be  poured  into  the  tube,  it  will  sink  through  the 
liquid  monoxide  and  immediately  be  solidified.  A  small  piece 


152 


ELEMENTS    OF    MODERN    CHEMISTRY. 


FIG.  62. 


of  incandescent  charcoal  let  fall  into  the  tube  will  float  upon 
the  surface  of  the  monoxide,  and  burn  with  great  brilliancy, 

notwithstanding  the  intense  cold 
by  which  it  is  surrounded,  as  evi- 
denced by  the  freezing  of  the 
mercury  (Fig.  62). 

Water  dissolves  about  its  own 
volume  of  nitrogen  monoxide  at 
ordinary  temperatures. 

A  taper  which  has  been  extin- 
guished, but  still  bears  a  spark 
of  fire,  is   relighted,  and  burns 
brilliantly  when  plunged  into  a 
jar  of  nitrous  oxide  (Fig.  63). 
In  the  same  manner,  the  combustion  of  sulphur  and  phos- 
phorus is  effected  with  great 
energy  in  an  atmosphere  of 
this  gas. 

Equal  volumes  of  nitrous 
oxide  and  hydrogen  form  a 
mixture  which  explodes  on 
the  passage  of  an  electric 
spark  or  on  the  application 
of  flame. 
N20  -f-  H2  =  H20  +  N2 

2222 
volumes,  volumes,   volumes,  volumes. 

Respiration  is  a  slow  com- 
bustion and  may  be  sustained 
for  a  few  seconds  by  nitrogen 
monoxide.  Such  inhalation 
does  not  suffocate  but  it  dis- 
turbs the  functions  of  the 
nervous  system,  producing 
anaesthesia,  and  for  this  pur- 
pose nitrous  oxide  is  now  largely  employed  by  surgeons  and 
dentists.  The  insensibility  is  frequently  preceded  by  a  stage 
of  intoxication,  hence  the  name  laughing-gas,  which  was  given 
by  Davy. 

It  must  be  added  that  these  exhilarating  effects  have  not 
been  observed  in  recent  experiments  upon  perfectly  pure  nitro- 
gen monoxide. 


FIG.  63. 


NITROGEN   DIOXIDE,  OR    NITRIC   OXIDE. 


153 


NITROGEN   DIOXIDE,   OR  NITRIC   OXIDE. 

Density  compared  to  air 1.039 

Density  compared  to  hydrogen 15. 

Molecular  weight  NO =-30. 

Preparation. — This  gas  was  discovered  in  1*7 72  by  Hales ; 
it  is  prepared  by  decomposing  cold,  dilute  nitric  acid  by  metallic 
copper. 

3Cu  -f  8HNO3  =  3Cu(N03)2  +  4H20     +  2NO 

Copper.          Nitric  acid.  Cupric  nitrate. 

The  copper  and  water  are  introduced  into  a  gas-bottle,  and 
ordinary  nitric  acid  is  added  by  means  of  a  funnel-tube  ;  the 
copper  is  immediately  attacked  and  dissolved,  forming  cupric 
nitrate  (Fig.  64),  and  at  the  same  time  nitric  oxide  gas  is  dis- 
engaged. This  gas  absorbs  oxygen  from  the  air  and  is  con- 


FIG.  64. 


verted  into  red  vapors,  which  are  at  first  apparent  in  the  gas- 
bottle,  but  as  the  evolution  of  nitric  oxide  continues,  the  gas 
in  the  flask  gradually  becomes  colorless,  and  may  then  be  col- 
lected in  jars  over  water. 

Properties. — Nitric  oxide  is  a  colorless  gas.  It  has  recently 
been  liquefied  by  Cailletet.  It  is  decomposable  by  heat,  but 
less  easily  than  the  monoxide.  It  is  scarcely  soluble  in  water, 
which  only  takes  up  a  twentieth  of  its  volume.  Its  most  charac- 
teristic property  is  the  energy  with  which  it  absorbs  half  its 
volume  of  oxygen,  passing  into  the  state  of  nitrogen  peroxide 
or  red  vapors, 
a* 


154  ELEMENTS   OF    MODERN    CHEMISTRY. 

If  a  jar  filled  with  nitric  oxide  be  opened  to  the  air,  the  red 
vapors  appear  at  once. 

2NO  -f  O2  =  N204 

Nitric  oxide  supports  the  combustion  of  certain  substances. 
Phosphorus  burns  in  it  brilliantly,  but  the  gas  does  not,  like 
oxygen  and  nitrogen  monoxide,  relight  a  taper  still  presenting 
a  spark. 

Hydrogen  decomposes  nitric  oxide  at  a  temperature  but 
slightly  elevated,  forming  water  and  nitrogen. 

NO  -f-  H2  =  N  -f  H20 

The  mixture  of  the  two  gases  in  equal  volumes  takes  fire  on 
the  application  of  flame. 

If  a  few  drops  of  carbon  disulphide  be  poured  into  a  jar  of 
nitric  oxide,  the  vapor  of  the  volatile  liquid  is  at  once  diffused 
throughout  the  gas,  and  on  the  approach  of  a  lighted  taper  a 
brilliant  flash  of  light  is  produced,  the  sulphur  and  carbon  being 
burned  by  the  oxygen  of  the  nitric  oxide. 

The  light  produced  by  this  combustion  determines  at  once, 
and  like  the  solar  light,  the  combination  of  chlorine  and  hydro- 
gen. 

When  a  mixture  of  nitric  oxide  with  an  excess  of  hydrogen 
is  passed  through  a  heated  tube  containing  platinum  sponge, 
water  and  ammonia  are  formed. 

NO  -f  5H  ==  H20  -f  NH3 

Under  other  circumstances  hydroxylamine  may  be  produced. 

A  solution  of  ferrous  sulphate  absorbs  nitric  oxide  with 
avidity,  assuming  a  dark-brown  color  ;  this  is  a  characteristic 
property,  by  which  nitric  oxide  may  be  recognized. 

NITROGEN   TRIOXIDE. 


This  compound  is  formed  when  a  mixture  of  nitric  oxide 
with  a  large  excess  of  oxygen  is  subjected  to  intense  cold.  It 
is  also  formed,  together  with  nitric  acid,  when  nitrogen  perox- 
ide is  treated  with  a  small  quantity  of  cold  water. 

2N*O*     -f     H2O    =     2HN03     -f     N203 

Nitrogen  peroxide.  Nitric  acid. 

It  is  a  blue  liquid,  which  boils  at  a  low  temperature. 


NITROGEN    PEROXIDE. 


155 


NITROGEN   PEROXIDE. 

NO2  or  N20* 

Preparation. — When  well  dried  lead  nitrate  is  heated  to 
redness  it  is  decomposed  into  lead  oxide  and  nitrogen  peroxide, 
which  may  be  condensed  in  a  well-cooled  receiver. 


Pb(N03)2     —     PbO 


0 


Lead  uitrate. 


Lead  oxide. 


The  first  portions  of  nitrogen  peroxide  that  are  condensed 
generally  retain  a  trace  of  moisture,  and  present  a  green  color ; 
if  the  receiver  be  then  changed,  there  collects  a  yellow  liquid 
which  solidifies  to  a  crystalline  mass  at  — 10°. 

Properties. — Nitrogen  peroxide  is  a  mobile  liquid,  almost 
colorless  at  very  low  temperatures ;  at  0°  it  has  a  somewhat 
darker  color,  and  at  15°  it  is  orange-brown.  It  boils  at  22°, 
and  its  vapor  is  red.  Near  the  point  of  ebullition  its  volu- 
metric composition  corresponds  to  the  formula  N20* ;  that  is, 
two  volumes  of  nitrogen  and  four  volumes  of  oxygen  are  con- 
densed into  two  volumes  of  N204,  and  occupy  the  same  space 
as  two  atoms  (one  molecule)  of  hydrogen. 

But  at  a  higher  temperature  this  vapor  is  dissociated  ;  that 
is,  it  is  gradually  decomposed  in  such  a  manner  as  to  occupy 
double  its  primitive  volume.  The  two  atoms  of  nitrogen  and 
four  atoms  of  oxygen  which  constitute  two  volumes  of  N20* 
at  a  low  temperature,  occupy  four  volumes  at  about  70°. 


NO2 


NO2 


NO2 


N|02 


Red  vapors  at  20°. 


Red  viipors  at  70°. 


The  vapor  of  nitrogen  peroxide  is  very  corrosive,  and  dan- 
gerous to  inhale. 

A  small  quantity  of  cold  water  decomposes  nitrogen  perox- 
ide into  nitrogen  trioxide  and  nitric  acid  ;  a  larger  quantity  of 
water  causes  the  formation  of  nitrous  and  nitric  acids. 


N204 


H20    = 


HNO2     -f 

Nitrous  acid. 


HNO3 

Nitric  acid. 


156  ELEMENTS   OF   MODERN   CHEMISTRY. 

When  a  mixture  of  nitrogen  peroxide  and  hydrogen  is  passed 
over  heated  platinum  sponge,  water  and  ammonia  are  formed. 

Nitryl  Chloride  and  Bromide.  —  Like  nitric  oxide,  which 
may  be  called  nitrosyl,  nitrogen  peroxide  may  play  the  part  of 
a  radical.  There  exists  a  chloride  and  also  a  bromide  of  nitro- 
gen peroxide  or  nitryl. 

N02C1  N02Br 

Nitryl  chloride.  Nitryl  bromide. 

The  latter  compound  is  formed,  together  with  other  products, 
when  bromine  acts  upon  nitrogen  peroxide  at  a  very  low  tem- 
perature. The  chloride  of  nitryl  has  recently  been  obtained 
by  the  reaction  of  phosphorus  oxychloride  upon  silver  nitrate. 

POCP     -f     3AgN03     ==     Ag3PO*     +     3(N02C1) 

Phosphorus  Silver  nitrate.          Silver  phosphate.          Nitryl  chloride. 

oxychloride. 


Nitryl  chloride  is  a  light-yellow  liquid,  boiling  at  -|-50  and 
solidifying  at  —  31°. 

In  contact  with  water,  it  forms  nitryl  hydrate  (nitric  acid), 
and  hydrochloric  acid. 

N02C1  +  H20  =  HC1  -j-  HNO3 

In  this  reaction,  the  nitric  acid  is  formed  at  the  expense  of 
the  water,  of  which  one  atom  of  hydrogen  is  removed  by  the 
chlorine  and  replaced  by  the  radical  nitryl.  Hence  nitric  acid 
and  water  may  be  said  to  belong  to  the  same  type  : 

HOH         (N02)OH 

Water.  Nitric  acid. 

It  is  seen  that  in  nitric  acid  the  group  NO2  replaces  one 
atom  of  hydrogen  in  water,  this  group  is  therefore  monatomic. 

But  the  atom  of  hydrogen  in  nitric  acid  may  also  be  replaced 
by  another  nitryl  group,  and  the  result  is  an  oxide  of  nitryl, 
the  anhydride  of  nitric  acid,  or  nitrogen  pentoxide.  The  fol- 
lowing formulae  will  illustrate  the  relations  between  these  com- 
pounds and  water  which  is  their  type  : 

Hlo         N°2lo         N°2 

H  }  C  H  |  C  NO2 

Water.  Nitric  acid.  Nitrogen  pentoxide. 

(Nitryl  hydrate.)  (Nitryl  oxide.) 


NITROGEN   PENTOXIDE  —  NITRIC   ACID.  15*7 

NITROGEN   PENTOXIDE. 
(NITRIC  ANHYDRIDE.) 


This  compound  was  obtained  by  H.  Sainte-Claire  Deville  by 
the  action  of  chlorine  upon  dry  silver  nitrate  heated  to  between 
58  and  60°. 

2AgN03     +     CP    =    N'O5     +     2AgCl     +     0 

Silver  nitrate.  Nitrogen  pentoxide.  Silver  chloride. 

It  may  also  be  obtained  by  passing  the  vapor  of  nitryl  chlo- 
ride over  silver  nitrate  heated  to  70°. 

AgO.NO2     -f     N02C1    =    AgCl     +     (N02)20. 

Silver  nitrate.  Nitryl  chloride.  Nitrogen  pentoxide. 

Also,  as  shown  by  Berthelot,  by  the  action  of  phosphorus 
pentoxide  upon  concentrated  nitric  acid. 

2HN03  —  H20  —  N205 

Nitrogen  pentoxide  is  solid  and  crystallizes  in  right-rhombic 
prisms.  It  melts  at  29.5°,  and  boils  between  48  and  50°.  It 
is  very  unstable  and  explodes  spontaneously  even  when  it  is 
preserved  at  a  low  temperature. 

NITRIC   ACID. 
HNQ3 

The  atmosphere  frequently  contains  a  trace  of  nitric  acid 
vapor  or  other  compounds  of  nitrogen  and  oxygen,  and  small 
quantities  of  ammonium  nitrate  and  nitrite  may  be  detected  in 
rain-water.  After  passing  a  current  of  air  for  a  long  time 
through  a  solution  of  potassium  carbonate,  the  liquid  is  found 
to  contain  potassium  nitrate  (Cloez).  It  may  be  admitted  that 
the  compounds  of  nitrogen  and  oxygen  are  formed  directly  by 
the  action  of  electricity  upon  the  elements  of  the  air.  * 

The  nitrates  of  potassium,  sodium,  magnesium,  and  calcium 
are  met  with  in  certain  soils,  often  in  abundance.  They  are 
formed  wherever  nitrogenized  organic  matters  decompose  in 
contact  with  the  air  and  in  presence  of  porous  matters  and 
alkaline  bases.  Under  these  circumstances,  the  ammonia  re- 
sulting from  the  decomposition  is  oxidized  to  nitric  acid. 

The  experiments  of  Cloez  have  shown  that  the  elements  of 

14 


158  ELEMENTS    OP    MODERN    CHEMISTRY. 

the  air  may  unite  directly,  forming  nitrates  in  the  soil,  wherever 
alkaline  bases  and  oxidizable  matters  are  present. 

Preparation.  —  Nitric  acid  is  obtained  by  decomposing  an 
alkaline  nitrate  with  sulphuric  acid.  In  the  laboratory,  the 
operation  may  be  conducted  in  a  glass  retort,  the  neck  of  which 
passes,  without  cork,  into  a  cooled  receiver.  98  parts  of  con- 
centrated sulphuric  acid  and  85  parts  of  sodium  nitrate  are 
employed.  On  the  application  of  heat,  nitric  acid  is  vola- 
tilized, mixed  at  the  commencement  of  the  operation  with  red 
vapors.  The  acid  condenses  in  the  receiver  as  a  yellow  liquid, 
fuming  in  the  air.  Sodium  acid  sulphate  remains  in  the  retort. 


H2SO     +     NaNO3     =     g     SO4     -f-     HNO3 

Sodium  nitrate.      Sodium  acid  sulphate. 

In  the  arts,  the  sodium  nitrate  is  decomposed  with  a  less 
concentrated  sulphuric  acid,  the  decomposition  of  the  nitric 
acid  during  the  operation  being  thus  avoided.  The  operation 
is  conducted  in  cast-iron  retorts,  A  (Fig.  65),  the  lateral  tubes 
of  which,  B,  are  adapted  to  stoneware  tubes  communicating 


Fio.  65. 

with  a  series  of  stoneware  bottles,  D,  where  the  acid  con- 
denses. The  temperature  is  elevated  towards  the  close  of  the 
operation,  and  sodium  neutral  sulphate  is  formed. 

H2SO*  -f  2NaN03  =  Na2S04  -f  2HN03 


NITRIC   ACID.  159 

Properties. — When  perfectly  pure,  nitric  acid  is  colorless, 
but  it  rapidly  becomes  yellow  under  the  influence  of  light, 
undergoing  a  partial  decomposition.  When  exposed  to  the 
air,  it  gives  off  abundant  white  fumes.  Its  density  is  1.52  ;  it 
solidifies  at  —49°,  and  boils  at  86°. 

When  its  vapor  is  passed  through  a  red-hot  porcelain  tube, 
it  is  decomposed  into  nitrogen  peroxide,  oxygen,  and  water. 

2HN03  —  H20  +  N204  +  0 

The  mixture  of  nitric  acid  with  water  produces  an  elevation 
of  temperature.  The  dilute  acid,  formed  by  mixing  42.8  parts 
of  water  and  100  parts  of  the  concentrated  acid,  is  a  colorless 
liquid,  boiling  constantly  at  123°  ;  yet  it  cannot  be  considered 
as  a  definite  compound  (Roscoe). 

Nitric  acid  readily  gives  up  a  portion  of  its  oxygen  to  bodies 
having  an  affinity  for  that  element.  It  energetically  oxidizes 
sulphur,  phosphorus,  arsenic,  iodine,  silicon,  carbon,  and  most 
of  the  metals. 

If  nitric  acid  be  poured  upon  red-hot  charcoal,  the  combus- 
tion is  vividly  intensified  by  the  decomposition  of  the  nitric 
acid,  and  red  fumes  appear  at  the  same  time. 

Copper  decomposes  nitric  acid  with  an  abundant  disengage- 
ment of  nitric  oxide,  which  is  converted  into  nitrogen  peroxide 
by  contact  with  the  air. 

Certain  metals  attack  the  dilute  acid  more  readily  than  the 
concentrated ;  iron  is  one  of  these  metals. 

If  dilute  nitric  acid  be  poured  upon  clean  iron  wire,  chemi- 
cal action  at  once  takes  place,  and  there  is  an  abundant  evolu- 
tion of  red  vapor  ;  but  if  the  same  wire  be  plunged  into  the 
concentrated  acid,  no  action  is  manifested ;  and  further,  if  the 
strong  acid  be  poured  off  and  replaced  by  dilute  acid,  the  latter 
undergoes  no  decomposition ;  the  iron  has  become  passive  by 
becoming  covered  with  a  thin  layer  of  gas.  But  if  its  surface 
be  touched  with  a  copper  wire,  chemical  action  is  at  once  re- 
established between  the  iron  and  the  nitric  acid. 

The  action  of  tin  upon  nitric  acid  is  worthy  of  notice.  Tor- 
rents of  red  vapor  are  disengaged,  and  the  metal  is  converted 
into  a  white  powder,  which  is  stannic  acid.  In  this  reaction 
small  quantities  of  ammonia  and  hydroxylamine  are  formed  at 
the  expense  of  the  elements  of  the  nitric  acid,  and  remain 
combined  with  the  excess  of  acid. 

The  conversion  of  nitric  acid  into  ammonia  may  be  more 


160  ELEMENTS    OP    MODERN   CHEMISTRY. 

complete.  If  zinc  be  introduced  into  very  dilute  nitric  acid, 
the  metal  dissolves  slowly  and  without  disengagement  of  gas ; 
the  liquid  is  then  found  to  contain  zinc  nitrate  and  ammo- 
nium nitrate.  The  nascent  hydrogen  set  free  from  a  portion 
of  the  nitric  acid  by  the  zinc  reduces  another  portion  of  the 
acid,  forming  water  and  ammonia. 

Zn  -f  2HN03  =  Zn(N03)2  +  H2 

Zinc.  Zinc  nitrate. 

2HN03  +  4H2  =  3H20  +    (NH4)N03 

Ammonium  nitrate. 

Nitrogen  dioxide  decomposes  nitric  acid.  When  a  current 
of  this  gas  is  passed  through  nitric  acid,  the  latter  becomes 
colored,  according  to  its  concentration,  brown,  yellow,  or  bluish- 
green.  Under  these  circumstances  the  acid  is  reduced,  and 
either  nitrogen  peroxide  or  nitrous  acid  is  formed  and  remains 
dissolved  in  the  liquid,  the  former  communicating  a  brown, 
the  second  a  blue  or  green  color. 

Nitric  acid  is  one  of  the  most  important  acids ;  it  is  largely 
used  as  a  reagent.  It  is  employed  in  the  manufacture  of  sul- 
phuric acid,  and  also  to  oxidize  certain  organic  matters,  such 
as  starch  and  sugar,  which  it  converts  into  oxalic  acid. 

Nitro-hydrochloric  Acid.— A  mixture  of  nitric  and  hydro- 
chloric acids  is  called  nitro-hydrochloric  or  nitro-muriatic  acid, 
or  aqua  regise.  This  liquid  dissolves  gold  and  platinum,  and 
it  owes  this  property  to  the  chlorine,  which  is  set  at  liberty  by 
the  mutual  action  of  the  two  acids. 

2HC1  +  2HN03  =  2H20  -f  N204  +  Cl2 

When  the  mixture  is  left  to  itself  it  gradually  assumes  a 
yellow  color,  undergoing  a  partial  decomposition,  as  indicated 
by  the  above  formula ;  but  this  decomposition  is  limited,  and 
only  complete  in  the  presence  of  a  metal  capable  of  absorbing 
the  chlorine. 

But  the  reaction  between  hydrochloric  and  nitric  acids  gives 
rise  to  the  formation  of  other  products,  noticed  by  Gay-Lussac 
and  Baudrimont ;  these  are  ternary  compounds  of  oxygen,  ni- 
trogen, and  chlorine.  One  is  a  red  vapor,  condensing  at  — 7° 
to  an  orange-red  liquid.  Its  composition  is  probably  expressed 
by  the  formula  NOC12. 

It  may  be  regarded  as  nitrogen  peroxide  in  which  one  atom 
of  oxygen  is  replaced  by  an  equivalent  quantity,  that  is,  two 
atoms,  of  chlorine. 


PHOSPHORUS.  161 

The  other  is  a  gas  which  does  not  liquefy  at  very  low  tem- 
peratures ;  it  is  nitrosyl  chloride,  NO.C1.  By  reacting'  with 
water  it  forms  hydrochloric  and  nitrous  acids. 

NO.C1  +  H20  =  HC1  +  NO.OH 

It  will  be  noticed  that  nitrosyl  chloride  bears  the  same  rela- 
tion to  nitrous  acid  that  nitryl  chloride  bears  to  nitric  acid. 
The  following  formulae  will  illustrate  the  constitution  of  these 
bodies : 

Nori  N0lo  N0lo 

H  {  L  NO  }  L 

Nitrcteji  chloride.  Nitrous  acid.  Nitrogen  trioxide. 

NO'Cl  N°2lo  N°2 

H  j  L  NO2 

Nitryl  chloride.  Nitric  acid.  Nitrogen  pentoxide. 


PHOSPHORUS 

Vapor  density  compared  to  air 4.32 

Vapor  density  compared  to  hydrogen    ....     61.1 
Atomic  weight  P =31. 

Brandt,  an  alchemist  of  Hamburg,  while  attempting  to  ex- 
tract the  philosopher's  stone  from  urine,  discovered  phosphorus 
in  1669.  But  urine  contains  only  a  small  quantity  of  phos- 
phates and  can  yield  but  traces  of  phosphorus,  so  that  this 
body  only  became  generally  known  to  chemists  after  Gahn 
demonstrated  its  existence  in  bones,  and  Scheele  discovered  the 
process  for  its  extraction. 

The  process  of  the  latter  chemist  is  still  in  use  ;  it  consists 
in  treating  bone-ash  with  dilute  sulphuric  acid,  by  which  means 
the  tricalcium  phosphate  of  the  bones  is  converted  into  mono- 
calcium  phosphate,  ordinarily  called  acid  phosphate  of  lime. 

Ca3(P04)2    +    2H2SO    =    CaH4(P04)2    +    2CaSO* 

Tricalcinm  Calcium  acid  Calcium 

phosphate.  phosphate.  sulphate. 

The  latter  phosphate  being  soluble  is  separated  from  the 
calcium  sulphate  by  filtration,  and  the  solution  is  evaporated 
and  mixed  with  powdered  charcoal.  The  mixture  is  dried  and 
gradually  heated  to  redness  in  cast-iron  vessels.  By  this  means 
the  calcium  acid  phosphate  is  converted  into  calcium  meta- 
phosphate  by  the  expulsion  of  two  molecules  of  water. 
CalP(PO)2  =  2H20  +  Ca(P03)2 

Calcium  acid  phosphate.  Calcium  metaphosphate. 


162 


ELEMENTS    OP    MODERN    CHEMISTRY. 


The  latter  is  strongly  heated  with  charcoal  in  clay  retorts 
(Fig.  66),  and  is  decomposed,  yielding  carbon  monoxide  and 
phosphorus  which  distils  over,  and  leaving  a  residue  of  calcium 
pyrophosphate. 


2Ca(P03)2 

Calcium 
metaphosplmte. 


+    50    = 


Ca2P207 

Calcium 
pyrcphosphate. 


5CO    + 

Carbon 

monoxide. 


p'2 


The  phosphorus  condenses  in  the  water  in  the  receiver  A, 
in  which  the  neck  of  the  retort  C  is  engaged. 


FIG.  66. 

As  it  is  impossible  to  expel  all  of  the  water  from  the  calcium 
acid  phosphate,  this  water  is  decomposed  by  the  charcoal,  hy- 
drogen and  carbon  monoxide  being  formed,  together  with  a 
small  quantity  of  phosphoretted  hydrogen. 

100  kilogrammes  of  bone  yield  between  8  and  9  kilo- 
grammes of  phosphorus.  The  latter  is  purified  by  enclosing 
it  in  a  chamois-skin  sack,  and  strongly  compressing  it  under 
water  at  50°  ;  the  phosphorus  passes  through  the  leather  and 
collects  under  the  water.  It  is  moulded  into  sticks  by  being 
drawn  up  into  slightly  conical  glass  tubes,  which  are  then 
plunged  into  cold  water.  The  phosphorus  solidifies  and  is 
easily  drawn  from  the  tubes. 

Physical  Properties. — Recently-fused  phosphorus  is  trans- 
parent, colorless,  or  having  a  pale-yellow  tint,  flexible,  and  soft 


PHOSPHORUS.  163 

enough  to  be  easily  scratched  by  the  nail.  One-tenth  per  cent, 
of  sulphur  renders  it  hard  and  brittle.  It  has  a  well-marked 
odor,  slightly  resembling  that  of  garlic.  Its  density  at  10°  is 
1.83.  It  melts  at  44°  and  boils  at  290°  ;  its  vapor  is  colorless 
and  has  a  density  of  4.32  compared  to  air,  or  61.1  compared 
to  hydrogen. 

If  one  volume  of  hydrogen  weighs  1,  one  volume  of  vapor 
of  phosphorus  weighs  61.1,  and  this  number  should  represent 
the  weight  of  one  atom  of  phosphorus ;  now  it  represents  the 
weight  of  two  atoms,  and  the  vapor  of  phosphorus  presents 
the  singular  anomaly  that  it  contains  in  the  same  volume 
twice  as  many  atoms  as  the  simple  gases,  such  as  hydrogen 
or  nitrogen.  If  one  volume  of  hydrogen  contain  one  atom, 
one  volume  of  phosphorus  vapor  contains  two,  and  heat  cannot 
dissociate  these  two  atoms  in  such  a  manner  that  they  may 
occupy  two  volumes  instead  of  one.  The  vapor  of  arsenic 
presents  the  same  anomaly. 


II 


P2 


As2 


1  volume  of  1  volume  of  1  volume  of  1  volume  of 

hydrogen.  nitrogen.  phosphorus  vapor.        arsenic  vapor. 

Phosphorus  volatilizes  below  its  boiling-point  and  even  below 
its  melting-point.  At  ordinary  temperatures  it  emits  vapors  in 
a  vacuum  and  even  in  the  air.  It  is  luminous  in  the  dark, 
from  which  property  it  derives  its  name,  which  signifies  light- 
bearer.  The  cause  of  this  phenomenon  is  still  obscure,  but  is 
generally  attributed  to  the  slow  oxidation  which  phosphorus 
undergoes  in  the  air. 

When  a  stick  of  transparent  phosphorus  is  kept  under  water, 
it  gradually  becomes  opaque  and  covered  with  a  yellowish-white 
pulverulent  powder,  while  the  central  parts  retain  their  trans- 
parence. This  white  phosphorus  is  still  pure,  but  the  surface 
of  the  stick  has  divided  into  a  multitude  of  little  particles  which 
present  a  crystalline  appearance.  Some  of  them  become  de- 
tached and  remain  suspended  in  the  water,  giving  to  the  latter 
the  property  of  being  luminous  in  the  dark. 

Phosphorus  is  rapidly  dissolved  by  carbon  disulphide  and  is 
deposited  in  rhombic  dodecahedra  on  the  slow  evaporation  of 
the  solution. 

There  is  an  amorphous  variety  of  phosphorus  which  differs 
so  much  from  ordinary  phosphorus  that  it  presents  the  prop- 


164  ELEMENTS   OF    MODERN    CHEMISTRY. 

erties  of  an  entirely  different  substance.  It  has  a  dark  brown- 
red  color,  and  is  not  luminous  in  the  dark.  It  is  insoluble  in 
carbon  disulphide ;  it  does  not  melt  and  take  fire  like  ordi- 
nary phosphorus  when  heated  to  50°.  It  is  amorphous,  and 
presents  a  conchoidal  fracture.  Its  density  is  2.14.  Ordinary 
phosphorus  is  one  of  the  most  dangerous  poisons,  but  this  red 
body  exerts  no  action  upon  the  economy.  At  260°  amor- 
phous phosphorus  melts,  is  converted  into  ordinary  phospho- 
rus, and  presents  the  properties  of  the  latter  substance  on 
cooling. 

Amorphous  phosphorus  results  from  a  physical  change 
brought  about  by  the  action  of  light  or  heat  on  the  ordinary 
variety.  If  a  stick  of  phosphorus  be  exposed  to  direct  sun- 
light, its  surface  assumes  a  red  color  ;  or  if  it  be  maintained 
for  a  long  time  at  a  temperature  of  240°,  it  is  entirely  con- 
verted into  the  amorphous  variety. 

This  transformation  is  also  accomplished  by  the  influence  of 
certain  chemical  agents.  If  a  small  stick  of  ordinary  phos- 
phorus be  introduced  into  a  test-tube  and  a  very  minute  por- 
tion of  iodine  be  allowed  to  fall  upon  it,  the  iodine  unites  with 
the  phosphorus  with  the  production  of  light  and  heat.  A  trace 
of  phosphorus  iodide  is  formed,  and  the  remainder  of  the  phos- 
phorus is  converted  into  a  hard,  black  mass,  which  yields  a  red 
powder  ;  this  is  amorphous  phosphorus  (E.  Kopp,  Brodie). 

Thus  prepared,  this  body  volatilizes  like  arsenic,  without 
melting,  and  can  be  distilled  without  alteration,  condensing  in 
a  black  mass,  which  contains  only  traces  of  iodine. 

Chemical  Properties, — Ordinary  phosphorus  possesses  a 
strong  affinity  for  oxygen.  When  exposed  to  the  air  it  slowly 
oxidizes,  and  the  slow  combustion,  aided  by  the  moisture  of  the 
air,  produces  a  mixture  of  phosphorous  and  phosphoric  acids. 
Schbnbein  has  shown  that  the  slow  oxidation  of  phosphorus 
is  accompanied  by  the  formation  of  small  quantities  of  ozone 
and  hydrogen  dioxide,  and  he  asserts  that  ammonium  nitrite  is 
formed  at  the  same  time. 

When  heated  in  the  air  to  a  temperature  of  60°,  phosphorus 
takes  fire  and  burns,  producing  a  bright  light  and  white  vapors 
of  phosphorus  pentoxide.  In  pure  oxygen  the  combustion  is 
accomplished  with  great  brilliancy. 

Phosphorus  may  be  burned  under  warm  water  by  passing  a 
current  of  oxygen  through  the  melted  element  by  means  of  a 
tube  drawn  out  to  a  point  (Fig.  67);  each  bubble  of  oxygen 


HYDROGEN    PHOSPHIDE.  165 

which  comes  in  contact  with  the  phosphorus  produces  a  bright 
flash. 

Phosphorus  takes  fire  spontaneously  in  an.  atmosphere  of  dry 
chlorine,  phosphorus  pentachloride  being  produced. 

Uses  of  Phosphorus. — This  body  is  principally  employed  in 
the  manufacture  of  matches.  The  inflammable  tips  of  friction- 
matches  contain  either  ordinary  or  amorphous  phosphorus.  In 
the  first  case,  the  phosphorus  is  mixed  with  inert  substances, 
such  as  sand  or  ochre,  held  together  by  strong  glue ;  in  the 


- 

FIG.  67. 

second  case,  the  ignition  of  the  amorphous  phosphorus,  which 
is  but  slightly  combustible,  is  determined  by  potassium  chlorate, 
to  which  is  also  added  antimony  sulphide.  All  of  these  sub- 
stances are  made  into  a  paste,  into  which  the  ends  of  the 
matches  are  dipped.  Sometimes  the  match-sticks  are  tipped 
with  a  paste  composed  of  potassium  chlorate  and  antimony 
sulphide,  a  mixture  which  only  takes  fire  by  friction  upon  a 
prepared  surface,  composed  generally  of  amorphous  phosphorus 
and  antimony  sulphide.  All  of  these  mixtures  are  held  to- 
gether by  strong  glue. 

HYDROGEN    PHOSPHIDE. 

Density  compared  to  air 1.134 

Density  compared  to  hydrogen 17. 

Molecular  weight  PH3 =  34. 

This  gas  was  discovered  by  Gengembre  in  1*783. 

When  phosphorus  is  heated  with  a  solution  of  caustic  potassa, 
there  is  a  gas  disengaged,  which  inflames  spontaneously  on  con- 
tact with  the  air ;  this  is  hydrogen  phosphide.  It  is  formed 
according  to  the  following  equation  : 

3KOH     +     4P     +     3H20     =     3KH2P02    +    PH3 

Potassium  hydrate.  Potassium  hypophoephite. 


166  ELEMENTS   OF   MODERN    CHEMISTRY. 

Preparation. — 1.  Hydrogen  phosphide  may  be  prepared  by 
heating  phosphorus  with  a  strong  solution  of  potassium  hydrate, 
or  with  thick  miljc  of  lime,  with  which  the  flask  (Fig.  68) 


FIG.  68. 

should  be  almost  entirely  filled.  The  gas  is  conducted  under 
the  surface  of  water,  and  as  each  bubble  arrives  in  contact  with 
the  air  it  takes  fire  spontaneously,  producing  a  bright  flash  and 
a  wreath  of  white  smoke,  which  enlarges  as  it  rises  in  the  air. 

2.  The  same  spontaneously  inflammable  gas  is  evolved  when 
calcium  phosphide  is  thrown  into  water  (Fig.  69).     The  phos- 
phide of  calcium  is  prepared  by  passing  vapor  of  phosphorus 
over  fragments  of  incandescent  lime ;  it  instantly  decomposes 
water  with  formation  of  calcium   hypophosphite  and  sponta- 
neously inflammable  hydrogen  phosphide. 

However,  when  calcium  phosphide  is  treated  with  hydro- 
chloric acid,  hydrogen  phosphide  is  produced,  which  does  not 
take  fire  without  the  application  of  heat  (Fig.  70). 

In  this  case,  the  gas  is  formed  by  double  decomposition 
between  the  hydrochloric  acid  and  the  calcium  phosphide  ;  the 
calcium  combines  with  the  chlorine,  forming  calcium  chloride, 
and  the  hydrogen  of  the  acid  combines  with  the  phosphorus. 

3.  In  the  same  manner,  when  phosphorous  acid  is  strongly 
heated  in  a  small  retort,  it  evolves  a  hydrogen  phosphide  which 
is  not  spontaneously  inflammable. 

4H3P03     =     PH3     +      3H8PO* 

Phosphorous  acid.  Phosphoric  acid. 


COMPOUNDS   OF   PHOSPHORUS   AND   CHLORINE.         167 


Properties, — The  gas  thus  obtained  is  colorless,  and  pos- 
sesses a  garlicky  odor.  It  is  but  slightly  soluble  in  water,  but 
is  soluble  in  alcohol  and  in  ether.  When  it  is  pure  it  does  not 
take  fire  in  the  air  at  a  temperature  below  100°,  and  then 
burns  with  a  very  luminous  white  flame.  According  to  Paul 
Thenard,  the  spontaneous  inflammability  of  the  hydrogen  phos- 
phide prepared  by  the  methods  first  mentioned  is  due  to  the 


FIG.  69. 


FIG.  70. 


presence  of  another  phosphide,  P'2H4 ;  this  is  a  very  volatile 
liquid,  extremely  inflammable,  and  the  least  trace  of  its  vapor 
in  hydrogen  phosphide  gas  communicates  to  the  latter  the 
property  of  spontaneous  inflammability. 

Hydrogen  phosphide  is  absorbed  by  a  solution  of  cuprie 
sulphate,  with  the  formation  of  black  phosphide  of  copper. 

The  composition  of  hydrogen  phosphide,  PH3,  recalls  that 
of  ammonia,  NH3,  and  the  analogy  between  the  two  gases  is 
further  revealed  by  the  property  common  to  both  of  uniting 
with  hydriodic  acid.  There  is  a  compound  of  hydrogen  phos- 
phide with  hydriodic  acid,  a  well-defined,  solid  body,  crystal- 
lizing in  brilliant  cubes. 

PII'.HI  or  PH4I  phosphonium  iodide. 

The  existence  of  a  solid  phosphide  of  hydrogen  has  been 
demonstrated,  and  the  formula  P2H  attributed  to  it. 

COMPOUNDS   OF  PHOSPHORUS  AND  CHLORINE. 
There  are  two  chlorides  of  phosphorus : 

Phosphorus  trichloride PCI3 

Phosphorus  pentachloride PCI4 


168  ELEMENTS   OF   MODERN    CHEMISTRY. 

There  are,  besides, 

Phosphorus  oxychloride POC13 

Phosphorus  sulphochloride PSC13 

PHOSPHORUS  TRICHLORIDE. 
PC1» 

When  a  current  of  dry  chlorine  is  passed  over  phosphorus 
heated  in  a  small  tubulated  retort,  a  liquid  compound  of  chlo- 
rine and  phosphorus  is  formed  and  may  be  condensed  in  a 
cooled  receiver.  This  is  phosphorus  trichloride.  It  is  a 
fuming,  colorless  liquid,  having  a  density  of  1.45  and  boiling 
at  74°. 

If  it  be  poured  into  water,  it  at  first  sinks  to  the  bottom, 
and  then  rapidly  disappears,  evolving  white  fumes  of  hydro- 
chloric acid,  and  forming  phosphorous  acid,  which  remains  in 
solution. 

POP  +  3H20  =  H3P03  +  3HC1 

PHOSPHORUS    PENTACHLORIDE. 
PCI* 

In  contact  with  an  excess  of  chlorine,  phosphorus  trichloride 
absorbs  two  more  atoms  of  that  gas,  and  condenses  into  a  yellow 
crystalline  solid,  phosphorus  pentachloride. 

This  body  is  volatile,  and  sublimes  without  fusion  when 
heated,  even  below  100°.  When  heated  under  pressure,  it 
melts  at  148°  and  boils  at  a  slightly  higher  temperature.  Its 
vapor  density,  taken  at  336°  and  reduced  to  0°,  is  equal  to 
3.656.  This  density  should  be  double,  supposing  that  the 
molecule  PCI5  occupies  two  volumes.  The  anomaly,  however, 
is  only  apparent,  for  there  are  good  reasons  for  believing  that 
at  the  temperature  336°  the  vapor  of  phosphorus  pentachloride 
no  longer  exists,  and  that  the  compound  is  decomposed  or  dis- 
sociated into  a  mixture  of  phosphorus  trichloride  and  chlorine, 
a  mixture  which  would  give  four  volumes  of  vapor  for  one 
molecule  of  PCI5. 

_      f  PCI3  =  2  volumes. 
:   {  Cl2      =  2  volumes. 
4  volumes. 

Indeed,  when  the  vapor  density  of  phosphorus  pentachloride 
is  taken  by  diffusing  it  in  the  vapor  of  the  protochloride,  which 


PHOSPHORUS   OXYCHLORIDE.  169 

prevents  the  dissociation  before  mentioned,  a  figure  is  found 
which  corresponds  very  nearly  with  the  theoretic  density  7.21 
(A.  Wurtz). 

Phosphorus  pentachloride  decomposes  water  with  energy, 
forming  hydrochloric  and  phosphoric  acids. 

PCI5  +  4H20  =  H3PO  +  5HC1 

When  only  a  small  quantity  of  water  is  present,  hydrochloric 
acid  is  disengaged,  by  the  exchange  of  two  atoms  of  chlorine 
for  one  atom  of  oxygen,  and  a  colorless  liquid  is  formed  which 
is  called  phosphorus  oxychloride.  When  heated  in  a  current 
of  hydrogen  sulphide,  phosphorus  pentachloride  is  converted 
into  the  sulphochloride,  a  colorless  liquid  boiling  at  126°. 

PCI5  +  H20  ==  2HC1  +        POCP 
PCI5  4-  H2S  =  2HC1  4-        PSCP 


PHOSPHORUS   OXYCHLORIDE. 

POCP 

This  body  is  readily  obtained  by  exposing  phosphorus  penta- 
chloride to  moist  air  until  it  becomes  liquid,  and  subsequently 
distilling  the  liquid  (A.  Wurtz).  It  is  formed  in  a  great  num- 
ber of  reactions  when  phosphorus  pentachloride  is  heated  with 
hydrated  acids,  such  as  oxalic  acid,  boric  acid,  etc.,  or  with 
oxides,  such  as  phosphoric  oxide.  In  these  cases,  one  atom  of 
oxygen  from  the  oxidized  body  is  exchanged  for  two  atoms  of 
chlorine  from  the  pentachloride  (Gerhardt). 

Phosphorus  oxychloride  is  a  colorless  liquid,  boiling  at  110°. 
When  poured  into  water,  it  sinks  and  is  at  once  decomposed, 
hydrochloric  and  phosphoric  acids  being  formed. 


POCP      +         H*°3  =  0'     +     3HC1 

Phosphorus  oxychloride.  3  molecules  water.    Phosphoric  acid. 

COMPOUNDS  OF   PHOSPHORUS   WITH    BROMINE 
AND  IODINE. 

Two  bromides  of  phosphorus  are  known  : 
Phosphorus  tribromide,  PBr3,  a  colorless  liquid. 
Phosphorus  pentabromide,  PBr5,  a  yellow,  crystalline  mass. 
To  the  trichloride  and  tribromide  of  phosphorus  there  cor- 
responds a  triiodide,  concerning  which  but  little  is  known. 
H  15 


1*70  ELEMENTS    OF   MODERN   CHEMISTRY. 

The  best  defined  and  most  important  combination  of  phos- 
phorus with  iodine  is  the  compound  P2I*. 

Phosphorus  Iodide,  P2I*. — This  body  is  obtained  by  dis- 
solving 26  parts  of  dry  phosphorus  in  30  or  40  times  its  weight 
of  carbon  disulphide,  and  gradually  adding  to  the  solution  203.4 
parts  of  iodine.  The  liquor,  at  first  reddish-yellow,  becomes 
orange-yellow ;  it  is  distilled  on  the  water-bath  to  drive  out  a 
part  of  the  carbon  disulphide,  and  on  cooling  it  deposits  a 
bright-red,  crystalline  mass.  This  is  the  iodide  P2I*. 

It  crystallizes  in  long,  brilliant,  flattened  needles,  which  are 
flexible,  and  melt  at  100°.  On  contact  with  water  it  is  decom- 
posed, forming  phosphorous  and  hydriodic  acids,  and  at  the 
same  time  depositing  a  yellow,  flocculent  precipitate  rich  in 
phosphorus  (Corenwinder). 


COMPOUNDS  OF  PHOSPHORUS  AND  OXYGEN. 

Phosphorus  combines  with  oxygen,  forming  two  oxides : 

Phosphorus  trioxide,  or  phosphorous  oxide      .     .     P203 
Phosphorus  pentoxide,  or  phosphoric  oxide     .     .     P205 

Each  of  these  oxides  can  combine  with  three  molecules  of 
water,  phosphorous  and  phosphoric  acids  being  thus  formed. 

P203  -f  3H20  =  2H3P03 
P205  -f  3H20  ==  2H3P04 

Besides  these  two  acids  there  is  another  containing  less  oxy- 
gen ;  it  is  hypophosphorous  acid,  whose  corresponding  oxide  is 
unknown.  These  three  acids  form  a  series  containing  for  three 
atoms  of  hydrogen  and  one  atom  of  phosphorus  regularly-in- 
creasing quantities  of  oxygen ;  they  may  be  said  to  constitute 
different  degrees  of  oxidation  of  hydrogen  phosphide. 

PH3  hydrogen  phosphide. 
PH30  (missing). 
PH302  hypophosphorous  acid. 
PH303  phosphorous  acid. 
PH304  phosphoric  acid. 

Constitution -of  the  Oxygen  Acids  of  Phosphorus. — Phos- 
phorous and  phosphoric  acids  are  related, — the  first  to  phos- 
phorus trichloride,  the  second  to  phosphorus  oxychloride.  In 


HYPOPHOSPHOROUS   ACID.  171 

fact,  they  are  derived  from  these  compounds  by  the  action  of 
water. 

P'"CP  phosphorus  trichloride. 
P(OH)3  phosphorous  acid  (phosphorus  trihydrate). 
(PO)'"C13  phosphorus  oxychloride  (phosphoryl  trichloride). 
(PO)'"(OH)3  phosphoric  acid  (phosphoryl  trihydrate). 

To  phosphorus  pentachloride,  PCI5,  would  correspond  a  pen- 
tahydrate,  P(OH  )5,  which  is  unknown.  Phosphoric  acid  would 
be  derived  from  the  latter  by  the  loss  of  a  molecule  of  water. 

P(OH)5  =  H20  +  (PO)(OH)3 

It  is  seen  that  in  phosphorous  acid,  as  in  the  trichloride,  phos- 
phorus is  regarded  as  playing  the  part  of  a  triatomic  element, 
while  it  is  pentatomic  in  the  pentachloride. 

In  hypophosphorous  acid,  it  must  be  admitted  that  one  atom 
of  hydrogen  is  united  directly  to  the  triatomic  phosphorus,  and 
its  constitution  is  expressed  by  the  formula 

H 
OH 

OH 
HYPOPHOSPHOROUS  ACID. 

H'PO2 

When  phosphorus  is  boiled  with  milk  of  lime  or  with  a  con- 
centrated solution  of  baryta,  a  soluble  hypophosphite  is  pro- 
duced, and  on  treating  the  solution  of  barium  hypophosphite 
with  sulphuric  acid,  a  precipitate  of  barium  sulphate  and  a 
solution  of  hypophosphorous  acid  are  obtained ;  they  may  be 
separated  by  filtration.  When  sufficiently  concentrated,  the 
liquor  leaves  a  colorless  and  very  acid  syrupy  residue,  which 
constitutes  hypophosphorous  acid. 

This  acid  is  decomposed  at  a  high  temperature,  yielding 
phosphoric  acid  and  hydrogen  phosphide.  It  is  gifted  with 
energetic  reducing  properties  :  it  instantly  decomposes  the  salts 
of  mercury  and  silver,  setting  free  the  metal.  An  excess  of 
hypophosphorous  acid  added  to  a  solution  of  cupric  sulphate 
precipitates,  by  the  aid  of  a  gentle  heat,  hydride  of  copper, 
Cu2H2,  which  is  decomposed  at  100°  into  copper  and  hydrogen 
(A.  Wurtz). 


172  ELEMENTS   OF   MODERN   CHEMISTRY. 

Hypophosphorous  acid  contains  three  atoms  of  hydrogen, 
only  one  of  which  is  capable  of  being  replaced  by  an  equiva- 
lent quantity  of  a  metal.  The  composition  of  the  hypophos- 
phites  is  consequently  expressed  by  the  following  general 
formula : 

R'H'PO* 

in  which  B/  represents  a  monatomic  metal,  such  as  potassium, 
capable  of  replacing  hydrogen  atom  for  atom. 


PHOSPHOROUS  ACID. 

H3PQ3 

Preparation. — Phosphorous  acid  results  from  the  action  of 
water  upon  phosphorus  trichloride,  as  already  seen.  It  may 
be  obtained  in  a  state  of  purity  by  evaporating  the  acid  liquor 
resulting  from  this  reaction,  and  heating  the  syrupy  residue 
in  a  platinum  capsule  until  the  odor  of  hydrogen  phosphide 
is  perceptible.  On  cooling,  the  acid  solidifies  to  a  crystalline 
mass. 

Properties. — These  crystals  absorb  moisture  when  exposed 
to  the  air,  and  are  resolved  into  an  intensely  acid  liquid ;  they 
melt  at  a  gentle  heat,  and  are  decomposed  by  a  high  tempera- 
ture into  hydrogen  phosphide  and  phosphoric  acid. 

Like  hypophosphorous  acid,  phosphorous  acid  possesses  re- 
ducing properties. 

Its  boiling  aqueous  solution  reduces  the  salts  of  mercury, 
silver,  and  gold,  and  this  reduction  is  favored  by  the  presence 
of  ammonia.  It  converts  arsenic  acid  into  arsenious  acid. 

Chlorine,  bromine,  and  iodine  convert  it  into  phosphoric  acid 
in  presence  of  water. 

H3P03  +  H2O  +  Cl2  =  2HC1  +  H3PO* 

Phosphorous  acid  contains  three  atoms  of  hydrogen,  two  of 
which  are  replaceable  by  an  equivalent  quantity  of  a  metal. 
It  is  hence  called  a  dibasic  acid. 

The  composition  of  the  neutral  hypophosphites  is  expressed 
by  the  general  formula 

ITHPO3, 

in  which  R'  represents  a  monatomic  metal  like  potassium  or 
sodium. 


PHOSPHORIC   OXIDE — PHOSPHORIC   ACID.  173 


PHOSPHORIC  OXIDE,  OR  PHOSPHORUS 
PENTOXIDE. 

(PHOSPHORIC  ANHYDRIDE.) 


This  compound  may  be  obtained  by  burning  phosphorus  in 
a  large  globe  filled  with  dry  air.  A  dense  white  smoke  is  pro- 
duced, and  condenses  upon  the  walls  of  the  vessel  in  flakes  like 
snow.  This  body  is  the  anhydride  of  phosphoric  acid.  When 
exposed  to  the  air,  it  absorbs  moisture  and  is  converted  into 
metaphosphoric  acid. 

_  H20  =  2HP03 


When  thrown  into  water  it  dissolves  with  a  hissing  noise, 
such  as  is  produced  by  a  red-hot  iron. 

Phosphoric  acid  volatilizes  at  a  dull-red  heat  ;  it  is  undecom- 
posable  by  heat.  It  yields  the  oxychloride  when  distilled  with 
phosphorus  pentachloride. 

P205  +  3PC15  =  5POC13 

It  also  yields  phosphorus  oxychloride  when  distilled  with 
dry  common  salt  (Lautemann). 

PHOSPHORIC  ACID. 

(ORTHOPHOSPHORIC   ACID.) 
H'PO* 

Preparation.  —  1.  This  acid  may  be  prepared  by  boiling 
phosphorus  with  nitric  acid.  On  account  of  the  violence  of 
the  reaction  the  operation  is  difficult  to  regulate,  and  even 
dangerous  when  ordinary  phosphorus  is  employed,  but  it 
succeeds  very  well  with  powdered  amorphous  phosphorus. 
This  is  heated  with  tolerably  concentrated  nitric  acid  in  a 
retort,  fitted  with  a  receiver,  and,  when  the  whole  of  the  phos- 
phorus has  disappeared,  a  little  nitric  acid  is  added  to  the 
contents  of  the  retort,  and  the  liquid  is  concentrated  in  a 
platinum  capsule.  When  the  last  portions  of  nitric  acid  have 
been  driven  out,  a  small  quantity  of  water  is  added,  and  the 
syrupy  liquid  is  placed  in  a  bell-jar  over  a  dish  containing 
concentrated  sulphuric  acid.  At  the  end  of  some  time,  the 

15* 


174  ELEMENTS   OF   MODERN   CHEMISTRY. 

phosphoric  acid  is  deposited  in  the  form  of  hard,  transparent, 
prismatic  crystals. 

2.  A  current  of  chlorine  may  be  passed  through  warm  water 
under  which  is  a  layer  of  melted  phosphorus.  Phosphoric 
acid  and  hydrochloric  acid  are  formed. 

PCI5  +  4H20  =  H3PO4  -f  5HC1 

As  soon  as  all  of  the  phosphorus  has  disappeared  the  solution 
is  evaporated,  and  the  hydrochloric  acid  is  driven  out  by 
heating  the  residue  to  200°.  The  residue  is  dissolved  in  water 
and  forms  a  solution  which  will  deposit  the  acid  in  crystals 
when  concentrated  as  indicated  above. 

Properties. — When  exposed  to  the  air,  these  crystals  attract 
moisture  and  deliquesce.  Their  solution  is  very  acid.  It  does 
not  coagulate  white  of  egg,  and  it  produces  no  cloud  in  a  solu- 
tion of  barium  chloride,  but  it  forms  a  white  precipitate  of 
ammonio-magnesium  phosphate  in  a  solution  of  magnesium 
sulphate  on  the  addition  of  ammonia.  With  silver  nitrate  to 
which  ammonia  has  been  added,  it  gives  a  yellow  precipitate 
of  trisilver  phosphate,  Ag3PO*.  Orthophosphoric  acid  contains 
three  atoms  of  hydrogen,  each  of  which  is  replaceable  by  an 
equivalent  quantity  of  metal. 

PYROPHOSPHORIC  ACID. 


When  orthophosphoric  acid  is  heated  for  a  long  time  to 
213°  it  loses  water  and  is  converted  into  a  new  acid,  which  is 
called  pyrophosphoric.  Two  molecules  of  phosphoric  acid  lose 
one  molecule  of  water,  and  then  unite  to  form  a  single  mole- 
cule of  pyrophosphoric  acid. 

/OH 

PO^-OH  /OH 

\^  TT  PO  vOH 

=  H20 

PO— OH 
PO^-OH 
XOH 

The  residue  constitutes  an  opaque,  semi-crystalline  mass, 
composed  almost  entirely  of  pyrophosphoric  acid. 


METAPHOSPHORIC   ACID.  175 

Its  aqueous  solution  forms  a  white  precipitate  of  silver 
pyrophosphate  in  solutions  of  silver  nitrate. 

H*P207 .+  4AgN03  ==  Ag4P207  +  4HN03 

When  heated  with  water,  pyrophosphoric  acid  again  com- 
bines with  one  molecule  of  that  liquid,  and  is  converted  into 
phosphoric  acid  by  a  reaction  the  inverse  of  that  by  which  it 
is  formed. 

METAPHOSPHORIC  ACID. 
HFC* 

Preparation. — When  phosphoric  acid  is  heated  to  redness 
in  a  platinum  crucible,  a  hard,  transparent,  vitreous  mass  is 
obtained  on  cooling ;  this  is  metaphosphoric  acid. 

It  is  formed  by  the  abstraction  of  one  molecule  of  water 
from  phosphoric  acid. 

H3PO*  —  H20  =  HPO3 

It  may  also  be  obtained  directly  from  calcium  acid  phos- 
phate, the  preparation  of  which  from  bone-ash  has  already  been 
described.  A  slight  excess  of  dilute  sulphuric  acid  is  added 
to  the  concentrated  solution  of  this  salt,  and  the  insoluble  cal- 
cium sulphate  formed  is  separated  by  nitration.  Since,  how- 
ever, the  calcium  sulphate  is  not  entirely  insoluble  in  water, 
the  solution  is  concentrated,  and  alcohol  added,  which  com- 
pletely precipitates  the  sulphate.  The  liquid  is  again  filtered, 
the  alcohol  driven  off  by  evaporation,  and  the  residue  heated 
to  a  temperature  near  redness  to  remove  the  excess  of  sulphuric 
acid. 

On  cooling,  a  vitreous  mass  of  metaphosphoric  acid  is  ob- 
tained. 

An  aqueous  solution  of  metaphosphoric  acid  instantly  pro- 
duces a  precipitate  of  silver  metaphosphate  in  a  solution  of 
silver  nitrate. 

HPO3  +  AgNO3  ===  AgPO3  -f  HNO3 

A  few  drops  of  the  acid  solution  added  to  white  of  egg  sus- 
pended in  water  produces  an  abundant  white  precipitate. 

The  same  metaphosphoric  acid  is  formed  when  phosphoric 
oxide  is  thrown  into  a  large  quantity  of  cold  water,  or  when  it 
is  allowed  to  deliquesce  in  the  air.  Under  these  circumstances, 


176  ELEMENTS    OF    MODERN    CHEMISTRY. 

one  molecule  of  phosphoric  oxide  combines  with  only  one 
molecule  of  water. 

P205  4-  IPO  =  2HP03 


The  preceding  considerations  establish  the  existence  of  three 
phosphoric  acids,  which  differ  both  in  composition  and  proper- 
ties. To  these  three  acids  correspond  three  salts  of  silver,  and 
it  will  be  seen  that  the  latter  differ  from  the  acids  only  by 
containing  silver  instead  of  hydrogen,  a  substitution  which 
takes  place  atom  for  atom. 

ACIDS.  SILVER     SALTS. 

H3PO*  phosphoric  acid  (orthophos-  Ag3P04  trisilver  phosphate  (ortho- 

phoric).  phosphate). 

H4P207  pyrophosphoric  acid.  Ag4P207  silver  pyrophosphate. 

HPO3  inetaphosphoric  acid.  AgPO3  silver  inetaphosphate. 

It  may  be  added  that,  independently  of  the  acids  and  salts 
of  which  the  composition  and  nomenclature  have  just  been 
considered,  others  have  been  described,  the  most  interesting 
of  which  are  related  to  the  metaphosphates,  of  which  they  con- 
stitute polymeric  modifications.  That  is,  two,  three,  four,  or 
more  molecules  of  metaphosphoric  acid  are  condensed  in  a 
single  molecule,  forming  more  complicated  acids. 

COMPOUNDS    OF    PHOSPHORUS  AND   SULPHUR. 

When  phosphorus  is  heated  with  dry  sulphur,  or  when  a 
mixture  of  the  two  bodies  is  melted  under  water,  they  combine 
with  a  vivid  combustion  which  is  sometimes  accompanied  by 
dangerous  explosions.  The  action  is  less  violent  with  amor- 
phous phosphorus.  According  to  the  proportions  of  these 
bodies  which  are  brought  into  contact,  several  combinations  of 
phosphorus  and  sulphur  may  be  obtained,  among  which  the 
trisulphide,  P2S3,  and  the  pentasulphide,  P2S5,  correspond  to 
phosphorous  and  phosphoric  oxides.  The  pentasulphide  may 
be  obtained  in  pale  yellow  crystals. 


ARSENIC. 

Vapor  density  compared  to  air 10.37 

Vapor  density  compared  to  hydrogen  ....     150. 
Atomic  weight  As =    75. 

Arsenic  was  discovered  by  A.  Schroeder  in  1694. 
Natural  State  and  Extraction. — There  exists  in  nature  a 


ARSENIC.  177 

common  and  abundant  mineral  which  contains  iron,  sulphur, 
and  arsenic,  and  which  is  called  mispickel ;  it  is  a  sulphar- 
senide  of  iron.  When  it  is  strongly  heated,  the  arsenic  is 
volatilized  and  a  residue  of  iron  sulphide  remains. 

FeSAs     =     FeS     +     As 

Mispickel.          Iron  sulphide. 

The  operation  is  conducted  on  the  large  scale  in  earthenware 
cylinders  placed  horizontally  in  a  furnace.  The  arsenic  sublimes 
into  sheet-iron  pipes  fitted  to  the  open  extremity  of  the  cylin- 
ders which  extend  beyond  the  furnace.  The  volatilization  of 
the  arsenic  is  facilitated  by  the  addition  of  a  certain  quantity 
of  metallic  iron. 

The  arsenic  of  commerce  may  be  purified  by  distilling  it  with 
charcoal  in  a  stoneware  retort. 

Properties. — Recently-sublimed  arsenic  presents  the  appear- 
ance of  a  steel-gray,  crystalline  mass,  having  a  metallic  lustre. 
Its  crystalline  form  is  an  acute  rhombohedron.  Its  density  is 
about  5.7. 

Arsenic  volatilizes  without  melting  at  a  temperature  below 
dull  redness.  Its  vapor  is  colorless.  When  it  is  heated  under 
strong  pressure  it  melts  to  a  transparent  liquid.  On  exposure 
to  the  air  it  loses  its  lustre  and  assumes  a  black-gray  color ;  in 
this  case  its  surface  becomes  covered  with  a  thin  layer  of  a 
brown-black  pulverulent  substance,  regarded  by  some  chemists 
as  a  suboxide  of  arsenic. 

Arsenic  oxidizes  when  it  is 
heated  in  the  air  or  in  oxygen. 

If  a  small  quantity  of  arsenic 
be  thrown  upon  a  red-hot  coal, 
white  vapors  are  produced,  and 
an  alliaceous  odor  is  percep- 
tible. 

A  fragment  of  arsenic  may 
be  strongly  heated  in  the  hori- 
zontal branch  of  a  tube  con- 
taining oxygen  (Fig.  71)  ;  the 
metal  takes  fire  and  burns  with 
bluish  flame,  producing  white  vapors  of  arsenious  oxide. 

If  arsenic  be  preserved  from  the  air  under  a  layer  of  water, 
in  which  it  is  insoluble,  it  oxidizes  slowly,  in  such  a  manner  as 
to  form  a  small  quantity  of  arsenious  acid,  which  dissolves  in 


178  ELEMENTS    OF    MODERN    CHEMISTRY. 

the  water.     This  property  explains  the  efficacy  of  powdered 
arsenic  (commercial  cobalt)  for  poisoning  flies. 

If  powdered  arsenic  be  sprinkled  into  dry  chlorine,  each 
particle  burns  with  a  bright  flash.  The  combustion  indicates 
the  energy  of  the  combination.  The  arsenic  unites  with  the 
chlorine,  being  converted  into  the  trichloride  AsCP.  It  also 
combines  directly  with  bromine,  with  iodine,  and  with  sulphur. 

HYDROGEN    ARSENIDE,  OR    ARSENIURETTED 
HYDROGEN. 

Density  compared  to  hydrogen 39. 

Molecular  weight  AsH3 =78. 

Preparation. — This  gas  may  be  prepared  by  the  action  of 
hydrochloric  acid  upon  zinc  arsenide. 

Zn3As2     -f     6HC1     =     2AsH3     +     3ZnCP 

Zinc  arsenide.  Zinc  chloride. 

It  is  a  gas  which  must  be  handled  with  great  prudence,  as  it 
is  extremely  poisonous. 

Properties. — Hydrogen  arsenide  is  colorless;  its  odor  is 
penetrating  and  garlicky.  At  a  red  heat  it  is  decomposed 
into  arsenic  and  hydrogen.  On  the  application  of  flame,  it 
burns  in  the  air  with  a  bluish  light,  producing  fumes  of 
arsenious  oxide.  If  the  supply  of  air  be  insufficient,  arsenic 
is  deposited.  With  one  and  a  half  times  its  volume  of  oxygen, 
hydrogen  arsenide  forms  an  explosive  mixture,  the  products  of 
the  combination  being  water  and  arsenious  oxide. 

2AsH3  -f  O6  =  As203  +  3H20 

Chlorine  decomposes  hydrogen  arsenide  with  a  production 
of  light  and  the  formation  of  hydrochloric  acid.  If  an  excess 
of  chlorine  be  present  arsenic  trichloride  is  formed,  but  if  the 
experiment  be  made  in  the  presence  of  water,  it  is  arsenious 
oxide  which  is  formed. 

2AsH3  -{-  6C12  +  3EPO  =  As203  -f  12HC1 

Water  dissolves  about  one-fifth  of  its  volume  of  hydrogen 
arsenide.  When  this  gas  is  agitated  with  a  solution  of  cupric 
sulphate,  it  disappears  entirely  if  the  gas  be  pure,  and  leaves 
a  residue  of  hydrogen  should  that  gas  have  been  present  in 
the  free  state  in  the  mixture  (Dumas). 

SCuSO4    -I-     2AsH3    =     Cu3As2     -f     3H2SO* 

Cupric  sulphate.  Copper  arsenide. 


ARSENIC   CHLORIDE. — ARSENIC-US   OXIDE.  1*79 


ARSENIC   CHLORIDE. 

AsCl3 

Preparation.  —  1.  A  current  of  dry  chlorine  may  be  parsed 
over  powdered  arsenic  contained  in  a  retort,  the  neck  of  which 
is  fitted  to  a  cooled  receiver.  The  chloride  formed  condenses 
as  a  yellow  liquid,  containing  an  excess  of  chlorine,  from  which 
it  may  be  freed  by  distillation  over  powdered  arsenic  (Dumas). 

2.  A  mixture  of  40  grammes  of  arsenious  oxide  and  400 
grammes  of  sulphuric  acid  is  gently  heated  in  a  tubulated 
retort,  and  fragments  of  fused  sodium  chloride  are  gradually 
added;  arsenic  chloride  distils  over  and  condenses  in  the 
receiver. 
3H2SO  -f  GNaCl  +  As203  =  3Na2SO  -f  2AsCl3  +  3H20 

Sodium  chloride.  Sodium  sulphate. 

Properties.  —  Arsenic  chloride  is  a  colorless,  oily,  and  very 
dense  liquid.  It  boils  at  134°.  Its  density  at  0°  is  2.05.  It 
gives  off  white  fumes  in  the  air,  and  is  very  poisonous. 

An  excess  of  water  instantly  decomposes  it  into  hydrochloric 
acid  and  arsenious  oxide,  which,  being  but  slightly  soluble,  is 
precipitated. 

2AsCl3  -|-  3H20  =  As203  +  6HCI 

ARSENIOUS   OXIDE. 


Preparation.  —  This  dangerous  poison  is  obtained  in  the 
arts  by  roasting  arseniferous  minerals,  particularly  mispickel. 
Roasting  is  an  operation  which  consists  in  heating  a  mineral 
in  contact  with  air,  by  which  the  oxidizable  elements  present 
are  oxidized.  When  arseniferous  minerals  are  roasted,  arsen- 
ious oxide  is  formed  among  other  products,  and  volatilizes,  and 
is  condensed  either  in  wide  horizontal  chimneys  or  in  a  large 
building  divided  into  numerous  communicating  compartments, 
through  which  the  vapor  is  led  consecutively.  It  is  collected 
in  the  form  of  a  powder,  and  is  resublimed  in  cast-iron  pots 
surmounted  by  sheet-iron  cylinders,  in  which  it  condenses. 

Properties.  —  Recently-sublimed  arsenious  oxide  occurs  as 
vitreous  masses  ;  but  it  soon  loses  its  transparency  and  becomes 
milk-white,  presenting  the  appearance  of  porcelain.  When  a 
large  piece  of  the  opaque  oxide  is  broken,  the  interior  is  usually 
found  to  be  still  transparent  and  vitreous. 


180  ELEMENTS   OF    MODERN    CHEMISTRY. 

Arsenious  oxide  then  exists  in  two  forms :  the  vitreous 
variety  is  amorphous ;  the  opaque  is  crystalline.  The  former 
variety  changes  into  the  latter  by  a  molecular  transformation 
which  takes  place  in  the  midst  of  the  amorphous  vitreous  mass. 

Arsenious  oxide  crystallizes  in  regular  octahedra  or  in  tetra- 
hedra ;  sometimes,  but  more  rarely,  in  right-rhombic  prisms. 
It  is  dimorphous. 

It  dissolves  slowly  in  cold  water,  in  which  it  is  but  slightly 
soluble,  and  in  this  respect  there  is  a  curious  difference  between 
the  opaque  and  the  vitreous  varieties.  The  latter  is  three  times 
more  soluble  than  the  former ;  while  one  part  of  the  vitreous 
oxide  dissolves  in  25  parts  of  water  at  13°,  one  part  of  the 
opaque  variety  requires  80  parts  of  water  for  its  solution  at  the 
same  temperature. 

The  aqueous  solution  of  arsenious  oxide  feebly  reddens  blue 
litmus.  It  is  almost  tasteless.  It  may  be  regarded  as  contain- 
ing normal  arsenious  acid,  H3As03,  corresponding  to  normal 
phosphorous  acid,  H3P03 ;  but  this  hydrate  cannot  be  separated 
from  the  solution.  On  evaporation,  the  oxide  As203  is  always 
deposited. 

2H3As03  =  As203  -f  3H20 

The  aqueous  solution  of  arsenious  oxide,  neutralized  with 
ammonia,  gives  a  green  precipitate  with  solution  of  cupric  sul- 
phate ;  this  is  copper  arsenite,  or  Scheele's  green.  With  silver 
nitrate  it  gives  a  canary-yellow  precipitate  of  silver  arsenite. 

Arsenious  oxide  is  more  soluble  in  hydrochloric  acid  than  in 
water.  If  a  slip  of  clean  copper  be  introduced  into  this  solu- 
tion, it  becomes  covered  with  a  steel-gray  or  black  coating  of 
arsenic. 

Reinsch's  test  for  arsenic  consists  in  boiling  the  suspected 
substance  with  dilute  hydrochloric  acid  and  bright  metallic 
copper.  The  arsenic  is  deposited  upon  the  copper,  and  by 
carefully  heating  the  latter  in  a  small  tube  the  arsenic  vola- 
tilizes and  is  converted  into  arsenious  oxide,  which  condenses 
in  the  crystalline  form,  easily  recognizable  by  aid  of  a  micro- 
scope. 

By  the  action  of  zinc  the  solution  of  As203  in  hydrochloric 
acid  disengages  hydrogen  arsenide ;  the  zinc  displaces  the  hy- 
drogen of  the  hydrochloric  acid,  and,  by  the  action  of  this 
nascent  hydrogen  upon  the  arsenious  oxide,  water  and  hydro- 
gen arsenide  are  formed. 

As203  -f  6H2  =  3H20  -f  2AsH3 


ARSENIOUS    OXIDE. 


181 


Marsh's  Apparatus, — The  reducing  action  of  nascent  hy- 
drogen upon  arsenious  oxide  is  used  for  the  detection  of  this 
substance  by  the  aid  of  Marsh's  apparatus. 

This  consists  of  an  apparatus  for  the  generation  of  hydrogen 
(Fig.  72) ;  it  contains  pure  zinc  arid  dilute  sulphuric  acid,  and  the 
hydrogen  burns  at  the 
drawn-out  jet  with  an 
almost  colorless  flame. 
If,  however,  a  few 
drops  of  a  solution  of 
arsenious  oxide  be  in- 
troduced by  the  fun- 
nel-tube, the  character 
of  the  flame  is  at  once 
changed ;  it  becomes 
bluish,  elongated,  and 
diffuses  a  white  smoke, 
and  if  a  white  porce- 
lain surface  be  de- 
pressed into  it,  large 
spots  of  a  brownish 
color  are  produced.  p 

These    are    composed 
of  arsenic,  which  is  set  free  in  the  interior  of  the  flame  by 
the  decomposition  of  the  hydrogen  arsenide  by  the  heat. 


FIG.  73. 

Fig.  73  represents  a  more  perfect  form  of  Marsh's  appa- 
ratus.   The  hydrogen,  mixed  with  the  hydrogen  arsenide,  first 

16 


182  ELEMENTS    OF    MODERN    CHEMISTRY. 

traverses  a  tube,  B,  filled  with  cotton,  designed  to  arrest  the 
small  drops  of  liquid  which  may  be  carried  with  the  gas  ;  it 
then  passes  through  a  narrow  tube  wrapped  with  metallic  foil 
and  heated  to  redness  in  a  tube-furnace.  The  hydrogen  arsen- 
ide is  decomposed  into  hydrogen  and  arsenic,  and  the  latter  is 
deposited  as  a  brilliant  black  mirror  in  the  cooler  portion  of 
the  tube. 

Marsh's  apparatus  permits  the  detection  of  the  least  trace 
of  arsenious  or  arsenic  acid  in  a  liquid.  It  is  of  great  value 
in  medico-legal  researches,  as  arsenious  oxide  is  a  common  and 
dangerous  poison. 

ARSENIC   ACID 


Preparation.  —  When  arsenious  oxide  is  heated  with  nitric 
acid  having  a  specific  gravity  of  1.35,  red  vapors  are  disen- 
gaged and  the  oxide  is  oxidized  into  arsenic  acid,  which  may 
be  obtained  as  a  syrupy  liquid  by  sufficient  concentration. 
When  left  for  a  long  time  in  a  cool  place  it  deposits  colorless 
crystals,  which  constitute  a  hydrate  2H3AsO*  -f  H2O  (E. 
Kopp).  These  crystals  are  very  deliquescent,  and  dissolve  in 
water  with  the  production  of  cold.  They  melt  at  100°,  losing 
their  water  of  crystallization,  and  there  remains  a  mass  com- 
posed of  fine  needles,  which  constitute  the  normal  acid 
H3AsO. 

When  heated  for  some  time  to  a  temperature  between  140 
and  180°,  this  acid  loses  water,  and  is  converted  into  pyro- 
arsenic  acid,  H4As207. 

2H3AsO  —  H20  =  H4As207 

Between  200  and  206°  another  quantity  of  water  is  driven 
out,  and  on  cooling  there  remains  a  pasty,  pearly  mass,  which 
is  metarsenic  acid,  HAsO3. 

H3AsO*  —  H20  =  HAsO3 

It  will  be  noticed  that  in  their  modes  of  formation  and  in 
their  constitution,  arsenic,  pyro-arsenic  and  metarsenic  acids  are 
analogous  to  the  corresponding  acids  of  phosphorus. 

When  metarsenic  acid  is  heated  to  dull  redness,  it  loses  all 
of  its  hydrogen  in  the  form  of  water,  and  is  converted  into 
arsenic  oxide,  As205. 

2HAs03  —  H20  =  As205 


COMPOUNDS   OF   SULPHUR   AND   ARSENIC.  183 

At  this  temperature  the  oxide  melts,  and  at  a  bright-red 
heat  it  is  decomposed  into  arsenious  oxide  and  oxygen. 

As205  =  As203  -f  O2 

When  exposed  to  the  air  it  absorbs  moisture,  but  very  slowly, 
and  even  when  treated  with  water  it  requires  a  certain  time  for 
solution. 

Ordinary  arsenic  acid,  which  may  be  called,  ortharsenic,  is 
very  soluble  in  water ;  its  solution  strongly  reddens  blue  litmus 
and  possesses  a  very  acid  taste.  It  is  reduced  by  nascent  hydro- 
gen, like  the  solution  of  arsenious  oxide.  When  neutralized 
with  ammonia,  it  forms  a  bluish-white  precipitate  with  solution 
of  cupric  sulphate,  and  a  brick-red  precipitate  with  silver 
nitrate.  Hydrogen  sulphide  produces  no  immediate  precipitate. 

A  solution  of  sulphurous  acid  reduces  arsenic  acid  to  arse- 
nious oxide,  and  then  on  the  addition  of  hydrogen  sulphide,  a 
yellow  precipitate  of  arsenic  sulphide,  As2S3,  is  formed. 

COMPOUNDS   OF  SULPHUR  AND  ARSENIC. 

Three  sulphides  of  arsenic  are  known: 

Arsenic  disulphide,  or  realgar As2S2 

Arsenic  trisulphide,  or  orpiment As?S3 

Arsenic  pentasulphide As2S5 

Arsenic  Bisulphide,  As2S2. — This  body  occurs  in  nature  in 
the  form  of  transparent  red  crystals,  which  belong  to  the  type 
of  the  oblique  rhombic  prism. 

It  is  obtained  as  a  red  mass  having  a  conchoidal  fracture  by 
melting  75  parts  of  arsenic  with  32  parts  of  sulphur.  It  is 
fusible,  and  may  be  crystallized  by  slow  cooling.  When  strongly 
heated  in  closed  vessels,  it  boils  and  distils  without  alteration, 
but  when  heated  in  the  air,  it  burns  into  arsenious  and  sulphur- 
ous oxides.  The  alkaline  sulphides  and  ammonium  sulphide 
dissolve  realgar,  leaving  a  brown  powder  which  has  been  con- 
sidered as  a  subsulphide  of  arsenic.  Boiling  solution  of  potas- 
sium hydrate  also  dissolves  realgar,  forming  a  mixture  of 
potassium  arsenite  and  sulpharsenite ;  the  latter  is  a  soluble 
compound  of  arsenic  trisulphide  and  potassium  sulphide;  a 
brown  powder  remains  undissolved. 

Arsenic  Trisulphide,  or  Orpiment,  As'2S3. — When  a  solu- 
tion of  arsenious  oxide  is  submitted  to  the  action  of  hydrogen 


184  ELEMENTS   OP   MODERN   CHEMISTRY. 

sulphide,  the  liquid  assumes  a  yellow  color  without  the  forma- 
tion of  any  precipitate,  but  if  a  drop  of  hydrochloric  acid  be 
added,  a  yellow,  flocculent  precipitate  of  arsenic  trisulphide  is 
formed  at  once. 

As203  +  3H2S  =  As2S3  -f  3H20 

The  composition  of  arsenic  trisulphide  corresponds  to  that 
of  arsenious  oxide,  and  is  the  same  as  that  of  the  orpiment 
found  in  nature. 

It  may  also  be  obtained  by  fusing  together  arsenic  and  sul- 
phur in  the  proper  proportions,  or  even  arsenious  oxide  and 
sulphur;  in  the  latter  case,  sulphurous  oxide  is  disengaged, 
and  arsenic  trisulphide  sublimes.  Thus  prepared,  orpiment 
occurs  as  crystalline  masses  of  a  yellow  color,  bordering  upon 
orange,  and  a  pearly  aspect.  Its  density  is  3.459.  It  is  fusible 
and  volatile. 

Arsenic  trisulphide  obtained  by  precipitation  is  insoluble  in 
cold  water,  and  but  slightly  soluble  in  boiling  water,  but  it  is 
very  soluble  in  ammonia.  By  continued  boiling  with  water,  it 
yields  hydrogen  sulphide  and  arsenious  acid  (de  Clermont 
and  Frommel).  It  is  also  dissolved  by  solutions  of  the  alka- 
line sulphides  with  the  formation  of  sulpharsenites,  compounds 
of  two  sulphides,  in  which  the  alkaline  sulphide  plays  the  part 
of  a  base  and  the  arsenic  trisulphide  the  part  of  an  acid. 
Orpiment  also  dissolves  in  solutions  of  the  caustic  alkalies  with 
the  formation  of  an  arsenite  and  a  sulpharsenite. 

Arsenic  Pentasulphide,  As2S5. — By  the  prolonged  action 
of  hydrogen  sulphide  upon  a  solution  of  arsenic  acid,  a  pale- 
yellow  precipitate  is  obtained,  which  is  arsenic  pentasulphide. 
2H3AsO  +  5H2S  —  As2S5  -f  8H20 

It  corresponds  to  arsenic  oxide. 

As205  As2S5 

Arsenic  oxide.  Arsenic  sulphide. 

The  alkaline  sulphides  dissolve  it  with  the  formation  of 
sulpharsenates.  Among  the  latter  there  is  one  having  the 
composition  K3AsS*,  and  which  corresponds  to  the  arsenate 
K3As04.  It  is  formed  by  the  following  reaction : 

As2S5  -f  3K2S  =  2(K3AsS4) 

The  existence  of  arsenic  pentasulphide  has  recently  been 
questioned,  the  precipitated  body  seeming  to  be  a  mixture  of 
trisulphide  and  sulphur  (de  Clermont  and  Frommel). 


ANTIMONY.  185 

ANTIMONY. 

Sb  =  122 

Antimony  is  generally  classed  with  the  metals.  It  indeed 
possesses  the  lustre  of  a  metal,  and  it  conducts  heat  and  elec- 
tricity; but  in  a  true  chemical  classification  these  physical 
properties  cannot  overbalance  the  most  striking  chemical  anal- 
ogies. By  its  affinities,  and  by  the  nature  and  constitution  of 
its  compounds,  antimony  must  find  a  place  by  the  side  of 
arsenic,  which  must  itself  be  classed  with  phosphorus  and 
nitrogen. 

Metallurgy  of  Antimony. — The  most  common  ore  of  anti- 
mony, which  is  a  sulphide,  was  known  to  the  ancients.  The 
metal  is  extracted  from  it  by  a  very  simple  process.  The  sul- 
phide is  first  separated  by  fusion  from  the  earthy  materials, 
called  gangue,  with  which  it  is  associated ;  it  is  then  roasted 
or  heated  in  contact  with  air.  The  sulphur  is  in  great  part 
expelled  in  the  form  of  sulphurous  oxide  gas,  and  the  antimony 
is  converted  into  oxide,  which  still  contains  some  undecom- 
posed  sulphide.  The  whole  is  then  pulverized,  and  the  pow- 
der mixed  with  pulverized  charcoal  impregnated  with  sodium 
hydrate.  This  mixture  is  calcined  in  crucibles,  and  the  anti- 
mony oxide  and  a  portion  of  the  sulphide  is  reduced  by  the 
charcoal ;  sodium  sulphide  is  also  formed,  and  this  dissolves  a 
portion  of  the  antimony  sulphide,  forming  a  flux  which  floats 
upon  the  molten  antimony ;  after  cooling,  the  latter  is  found 
at  the  bottom  of  the  crucible  as  a  button,  easy  to  separate  from 
the  scoriae. 

By  another  process  the  antimony  sulphide  is  fused  with 
metallic  iron.  Iron  sulphide  and  antimony  are  formed,  and 
the  latter  collects  at  the  bottom  by  reason  of  its  greater 
density. 

Perfectly  pure  antimony  is  prepared  in  the  laboratory  by 
reducing  antimonous  or  antimonic  oxide  by  charcoal. 

Properties. — Antimony  is  a  brilliant  white  metal,  having  a 
slightly  bluish  lustre ;  it  is  brittle,  and  has  a  laminated  frac- 
ture. Its  density  is  6.715.  It  melts  at  about  450°,  and 
sensibly  vaporizes  at  a  white  heat. 

Antimony  may  be  crystallized  by  allowing  large  masses  of 
the  fused  metal  to  cool  slowly,  and  decanting  the  liquid  por- 
tion. Small  acute  rhombohedra  may  be  obtained  in  this 
manner. 

16* 


186  ELEMENTS   OP   MODERN   CHEMISTRY. 

When  heated  in  contact  with  air.  antimony  is  converted 
into  antimonous  oxide,  Sb203. 

If  a  fragment  of  antimony  be  introduced  into  a  cavity 
scraped  in  a  piece  of  charcoal,  and  the  flame  of  a  blow-pipe  be 
directed  upon  it,  it  melts,  becomes  red-hot,  and  gives  off  white 
fumes.  If  now  the  molten  globule  be  allowed  to  fall,  it 
breaks  up  into  a  multitude  of  smaller  globules  on  striking  the 
floor,  and  each  particle  rebounds  into  the  air  as  a  brilliant 
spark,  leaving  behind  it  a  train  of  smoke. 

Powdered  antimony  projected  into  dry  chlorine  unites  with 
that  element,  producing  a  brilliant  combustion. 

HYDROGEN   ANTIMONIDE. 

There  is  a  compound  of  hydrogen  and  antimony  which  has 
not  yet  been  obtained  in  the  pure  state,  but  which,  according 
to  all  probability,  is  the  body  SbH3.  Like  its  analogue,  hy- 
drogen arsenide,  it  is  decomposed  by  heat ;  it  can  also  be  pre- 
pared in  Marsh's  apparatus  by  the  action  of  nascent  hydrogen 
upon  a  solution  containing  antimony,  and  when  decomposed 
by  heat  it  forms  metallic  rings  and  mirrors,  which  it  is  of  im- 
portance to  distinguish  from  those  formed  by  arsenic.  The 
following  differences  are  sufficient  for  this  purpose: 

The  antimony  rings  are  not  displaced  when  heated  in  a 
current  of  hydrogen ;  the  arsenic  rings  are  volatilized,  and 
condense  in  a  cooler  portion  of  the  tube. 

The  spots  and  rings  of  antimony  are  not  dissolved  by  a  solu- 
tion of  sodium  hypochlorite  (Labarraque's  solution),  which  at 
once  dissolves  those  of  arsenic. 

The  antimony  spots  are  readily  dissolved  by  a  drop  of  nitric 
acid,  and  the  liquid  leaves  on  evaporation  a  white  residue, 
which  is  not  colored  by  the  addition  of  a  drop  of  silver  nitrate 
solution.  Under  the  same  circumstances,  the  arsenical  spots 
leave  a  white  residue,  which  assumes  a  brick-red  color  when 
moistened  with  a  solution  of  silver  nitrate,  owing  to  the  for- 
mation of  silver  arsenate. 

COMPOUNDS   OF  ANTIMONY  AND   CHLORINE. 

Two  chlorides  of  antimony  are  known : 

Antimony  trichloride SbCl3 

Antimony  pentachloride SbCl5 

Antimony  Trichloride,  SbCl3. — This  compound,  formerly 


COMPOUNDS   OF   OXYGEN    AND   ANTIMONY.  187 

known  as  butter  of  antimony,  is  formed  by  the  action  of  hy- 
drochloric acid  upon  antimony  sulphide.  It  is  generally  pre- 
pared in  the  laboratory  from  the  residue  from  the  preparation 
of  hydrogen  sulphide.  This  acid  liquid  is  distilled  in  a  retort 
provided  with  a  receiver,  which  is  changed  as  soon  as  the  anti- 
mony chloride  which  distils  over  begins  to  crystallize  in  the 
neck  of  the  retort. 

This  chloride  is  solid,  transparent,  and  colorless.  It  melts 
at  73.2°,  and  boils  at  230°.  It  dissolves  in  water  charged 
with  hydrochloric  acid,  forming  a  colorless  solution,  but  when 
this  liquid  is  diluted  with  water  there  is  formed  an  abundant 
white  precipitate,  long  known  as  powder  of  Algaroth.  It  is 
an  oxychloride  of  which  the  composition  does  not  appear  con- 
stant. There  is  one  which  contains  SbOCl,  and  which  can  be 
regarded  as  antimony  trichloride,  in  which  two  atoms  of  chlo- 
rine have  been  replaced  by  one  atom  of  oxygen. 

It  is  form  3d  by  a  double  decomposition,  according  to  the 
following  reaction : 

SbCP  +  H20  —  2HC1  -f  SbOCl 

Antimony  Pentachloride,  SbCl5.— This  is  formed  by  the 
action  of  an  excess  of  chlorine  upon  antimony  or  upon  the 
trichloride.  It  is  a  yellow  liquid,  giving  off  white  fumes  in  the 
air.  It  is  volatile,  but  cannot  be  distilled  without  undergoing 
a  partial  decomposition  into  chlorine  and  antimony  trichloride. 
When  exposed  to  the  air,  it  absorbs  moisture  and  is  converted 
into  a  crystalline  mass,  which  is  a  hydrate  of  the  pentachloride. 
When  treated  with  a  large  excess  of  water,  it  is  decomposed 
with  production  of  heat,  and  formation  of  pyrantimonic  and 
hydrochloric  acids. 


COMPOUNDS  OF   OXYGEN   AND   ANTIMONY. 

Two  oxides  of  antimony  are  known,  corresponding  to  those 
of  phosphorus  and  arsenic  : 

Antimonous  oxide Sb2Q3 

Antiinonic  oxide Sb205 

Normal  antimonic  acid,  H3SbO*,  corresponding  to  phosphoric 
and  arsenic  acids,  is  not  known  in  the  free  state,  but  a  derivative 
of  this  acid  exists  and  may  be  regarded  as  antimony  antimonate. 
Its  composition  is  Sb204,  and  it  is  derived  from  antimonic  acid 


188  ELEMENTS   OP   MODERN   CHEMISTRY. 

by  the  substitution  of  an  atom  of  antimony  for  three  atoms  of 
hydrogen. 

H3Sb04  antimonic  acid. 
SbSbO*  antimony  antimonate. 

There  is  a  pyrantimonic  and  also  a  metantimonic  acid, 
analogous  to  the  corresponding  phosphorus  acids : 

H4Sb207  pyrantimonic  acid. 
HSbO3  metantimonic  acid. 

ANTIMONOUS   OXIDE. 

Sb203 

This  is  obtained  by  oxidizing  the  metal  in  the  air.  The 
operation  may  be  conducted  in  two  crucibles  placed  one  above 
the  other,  an  opening  being  pierced  in  the  upper  one  for  the 
access  of  air.  They  are  heated  to  redness  in  a  furnace,  and  on 
cooling,  the  antimony  is  found  to  be  partially  converted  into 
brilliant  needles  that  the  ancients  called  silver  flowers  of  anti- 
mony. The  crystals  are  right  rhombic  prisms,  mixed  with 
regular  octahedra,  for  antimonous  oxide  crystallizes  in  two 
forms,  presenting  the  same  character  of  dimorphism  as  arsenious 
oxide.  The  two  compounds  are  hence  said  to  be  isodimorphous. 

When  solution  of  sodium  hydrate,  or  better,  sodium  carbon- 
ate, is  poured  into  solution  of  antimony  trichloride,  a  white 
precipitate  of  antimonous  hydrate  is  formed,  and,  in  the  latter 
case,  carbonic  acid  gas  is  disengaged. 

SbCP     +     3NaOH     =     H3Sb03      -f      SNaCl 

Sodium  hydrate.      Antimonous  hydrate.      Sodium  chloride. 

This  hydrate  readily  parts  with  a  molecule  of  water,  being 
converted  into  another  hydrate,  HSbO2. 

H3Sb03  —  H20  =  HSbO2 

ANTIMONY   ANTIMONATE. 

Sb20 

This  compound  is  formed  when  antimonous  oxide  is  heated 
for  a  long  time  in  the  air,  oxygen  being  absorbed,  or  when 
antimonic  oxide  is  strongly  calcined,  oxygen  being  then  disen- 
gaged. 

It  is  a  white,  infusible  powder,  undecomposable  by  heat  and 
insoluble  in  water. 


ANTIMONIC   OXIDE   AND    ACIDS.  189 

ANTIMONIC   OXIDE   AND   ACIDS. 

When  powdered  antimony  is  heated  with  concentrated  nitric 
acid,  a  white  powder  is  obtained,  which  is  metantimonic  acid. 
It  contains  one  atom  of  hydrogen  capable  of  being  replaced  by 
an  equivalent  quantity  of  metal,  and  thus  corresponds  to  meta- 
phosphoric  acid. 

HPO3  HSbO3  KSbO3 

Metaphosphoric  acid.    Metantimonic  acid.    Potassium  metantimonate. 

When  it  is  heated  to  dull  redness,  it  loses  water  and  is  con- 
verted into  antimonic  oxide. 

2HSb03  —  H20  t=  Sb205 

If  antimony  pentachloride  be  poured  into  an  excess  of 
water,  a  white  precipitate  of  pyrantimonic  acid  is  formed. 
It  is  the  analogue  of  pyrophosphoric  acid,  and,  like  the  latter, 
contains  four  atoms  of  hydrogen. 

H*P207  H4Sb207  K*Sb207 

Pyrophosphoric  acid.         Pyrantimonic  acid.      Potassium  pyrantimonate. 

According  to  Fremy,  potassium  pyrantimonate  may  be 
obtained  by  heating  metantimonic  acid  or  potassium  metanti- 
monate with  potassium  hydrate,  in  a  silver  crucible. 

2KSb03     +     2KOH     =    K4Sb2O7     -f     H2O 

Potassium  Potassium  Potassium 

metantimonate.  hydrate.  pyrantimonate. 

The  metantimonate  may  be  extracted  by  water,  in  which  it 
is  soluble,  from  the  white  mass,  called  by  the  ancients  dia- 
phoretic antimony,  which  is  obtained  by  deflagrating  in  a  red- 
hot  crucible  a  mixture  of  2  parts  of  nitre  (potassium  nitrate) 
and  1  part  of  powdered  antimony.  Cold  water  first  dissolves 
potassium  nitrate  from  this  mass,  and  then  potassium  metanti- 
monate. The  solution  of  the  latter  salt  produces  with  hydro- 
chloric acid  a  white  precipitate  of  metantimonic  acid. 

SULPHIDES   OF   ANTIMONY. 

Two  sulphides  of  antimony  are  known  : 

Antimony  trisulphule,  or  antimonous  sulphide       .     .     Sb2S3 
Antimony  pentasulphide,  or  antimonic  sulphide    .     .     Sb2S5 

Antimonous  Sulphide,  Sb2S3. — This  compound,  ordinarily 
called  sulphide  of  antimony,  occurs  both  in  the  crystalline 


190  ELEMENTS   OF   MODERN   CHEMISTRY. 

form  and  amorphous.  Crystallized,  it  exists  in  nature  and  is 
the  mineral  commonly  known  as  stibium.  It  is  separated  from 
its  gangue  by  fusion,  and  is  thus  obtained  in  gray  masses  com- 
posed of  brilliant  needles  having  a  metallic  lustre. 

Amorphous,  it  constitutes  the  orange-colored  precipitate 
formed  by  the  action  of  hydrogen  sulphide  upon  a  solution  of 
antimony  chloride.  This  precipitate  is  insoluble  in  ammonia, 
but  dissolves  in  ammonium  sulphide  and  in  the  alkaline  sul- 
phides. 

Antimony  trisulphide  is  reduced  by  hydrogen  at  a  high 
temperature ;  hydrogen  sulphide  is  formed,  and  metallic  anti- 
mony remains. 

When  heated  in  the  air,  antimony  sulphide  is  oxidized  with 
formation  of  sulphurous  oxide  and  antimonous  oxide.  The 
incompletely  roasted  residue  melts  at  a  red  heat,  and  on  cool- 
ing assumes  the  form  of  a  brown  vitreous  mass  called  glass 
of  antimony.  It  is  an  impure  oxysulphide  which  appears  to 

contain  the  compound  Sb2S20  =  g^g  j  0. 

Antimony  Pentasulphide,  Sb'2S5. — When  finely-pulverized 
antimony  trisulphide  is  digested  with  sulphur  and  a  solution 
of  sodium  hydrate,  or  a  mixture  of  sulphur,  sodium  carbonate, 
and  lime,  the  antimony  sulphide  gradually  dissolves  in  the 
liquid,  combining  both  with  sulphur  and  with  the  sodium  sul- 
phide formed.  The  product  of  the  reaction  is  a  sulphantimo- 
nate  of  sodium,  which  is  deposited  in  fine  crystals  from  'the 
concentrated  liquid. 

Sb2S5     +       3Na2S       =         2Na3SbS4 

Sodium  sulphide.        Sodium  sulphantimonate. 

The  crystals  of  this  compound  contain  9  molecules  of  water 
of  crystallization.  It  corresponds  to  the  sulpharsenate  already 
mentioned,  and  to  trisodium  phosphate,  Na3P04. 

It  is  soluble  in  water,  and  on  the  addition  of  hydrochloric 
acid  to  its  solution,  hydrogen  sulphide  is  disengaged  and  anti- 
mony pentasulphide  is  precipitated. 

2Na3SbS*       6HC1  =  GNaCl       Sb2S5       3H2S 


General  Considerations  upon  the  Elements  of  the  Nitro- 
gen Group. — Nitrogen,  phosphorus,  arsenic,  and  antimony, 
and  bismuth  might  be  added,  form  a  group  of  elements  allied 
by  the  most  striking  analogies.  This  is  made  manifest  by  the 


BORON. 


191 


atomic  composition  of  their  compounds,  as  will  be  seen  in  the 
following  synopsis : 

HYDROGEN   COMPOUNDS. 

NH3  PH3  AsH3  SbH3 

Ammonia.    Hydrogen  phosphide.    Hydrogen  arsenide.    Hydrogen  antimonide. 


NCI3 

Nitrogen 
trichloride. 


CHLORINE   COMPOUNDS. 

PCI3  AsCl3 

Phosphorus 
trichloride. 

PCI5 


Arsenic 
trichloride. 


SbCP 

Antimony 
trichloride. 

SbCl5 


Phosphorus  pentachloride. 

OXYGEN    COMPOUNDS. 


Antimony  pentachloride. 


As*O  Sb203 

Nitrogen  trioxide.    Phosphorous  oxide.    Arsenious  oxide.  Antimonous  oxide. 

N205  P205  As'O  Sb205 

Nitrogen  pentoxide.    Phosphoric  oxide.      Arsenic  oxide.  Antimonic  oxide. 


H3P04 

Phosphoric  acid. 


H3P03  H3As03  H3Sb03 

Phosphorous  acid.      Arsenious  acid.       Antimonous  acid. 

HNO2  —  HSbO2 

Nitrous  acid.  Antimony  I  hydrate. 

H3As04 

Arsenic  acid. 

H4As207  H4Sb207 

Pyrophosphoric  acid.  Pyro-arsenic  acid.   Pyro-antimonic  acid. 

HNO3  HPO3  HAsO3  HSbO3 

Nitric  acid.    Metaphosplioric  acid.     Metarsenic  acid.      Metantimonic  acid. 

If  the  analogy  between  nitrogen  and  phosphorus  were  com- 
plete, there  should  be  an  orthonitric  acid,  H3N04  =  HNO3  -f- 
H20,  corresponding  to  ordinary  or  orthophosphoric  acid.  This 
acid  is  not  known  as  a  definite  hydrate,  but  compounds  exist 
which  are  derived  from  it.  Thus,  bismuth  subnitrate,  BiNO4, 
can  be  regarded  as  a  salt  of  orthonitric  acid,  in  which  three 
atoms  of  hydrogen  are  replaced  by  one  atom  of  triatomic 
bismuth. 


BORON. 

Bo  =  11 

Boron  is  the  radical  of  boric  acid.  It  exists  in  the  amor- 
phous state  and  crystallized.  It  was  discovered  by  Gay-Lussac 
and  Thenard  in  1808. 


192  ELEMENTS    OF    MODERN    CHEMISTRY. 

Preparation.  1.  Amorphous  Boron, —  Boric  oxide  is  re- 
duced by  sodium  at  a  red  heat,  and  the  cooled  mass  is  treated 
with  dilute  hydrochloric  acid.  The  sodium  borate  which  is 
formed  is  thus  dissolved,  and  a  residue  consisting  of  amorphous 
boron  is  obtained  as  a  dark  powder. 

2Bo203     +     3Na2     =     2Na3Bo03    +     Bo2 

Boric  oxide.  Sodium.  Sodium  borate. 

2.  Crystallized  Boron. — Boric  oxide  is  fused  with  alumin- 
ium ;  a  part  of  this  metal  reduces  the  boric  oxide  and  becomes 
oxidized,  while  another  part  dissolves  the  boron  set  free,  and 
again  deposits  it  in  the  crystalline  form  on  cooling  (H.  Sainte- 
Claire  Deville), 

Al2  +  Bo203  =  APO3  +  Bo2 

Properties. — Amorphous  boron  is  a  dark-brown  powder,  or 
brown  bordering  upon  green.  It  is  infusible.  Heated  to  300° 
in  the  air,  it  burns,  being  converted  into  boric  oxide.  Its 
combustion  in  pure  oxygen  is  very  brilliant.  Amorphous 
boron  possesses  a  singular  affinity  for  nitrogen.  At  a  red  heat 
it  absorbs  this  gas,  forming  a  nitride  of  boron,  BoN.  When 
heated  to  dull  redness  in  an  atmosphere  of  nitrogen  dioxide,  it 
burns  into  a  mixture  of  boric  oxide  and  boron  nitride  (Wohler 
and  Deville). 

Crystallized  boron  occurs  as  square  octahedra  (Sella).  In 
this  form  it  is  almost  as  hard  as  the  diamond,  and  will  scratch 
rubies.  The  color  of  the  crystals  varies  from  yellow  to  deep 
garnet-red;  sometimes  they  appear  black.  Their  density  is 
2.63. 

Crystallized  boron  energetically  resists  oxidation,  both  when 
it  is  heated  in  oxygen  and  when  it  is  subjected  to  the  action  of 
fused  potassium  nitrate.  At  a  bright-red  heat  it  reacts  upon 
potassium  acid  sulphate,  sodium  hydrate,  and  sodium  carbonate. 
It  burns  in  chlorine  at  a  red  heat. 

BORON   CHLORIDE. 

BoCl3 

Preparation. — This  body,  which  was  discovered  by  Berze- 
lius,  is  prepared  by  Wb'hler  and  Deville  by  heating  perfectly 
dry,  amorphous  boron  in  a  current  of  chlorine  gas,  and  passing 
the  vapor  of  boron  chloride  formed  into  a  receiver  surrounded 
by  a  mixture  of  ice  and  salt. 


BORON   FLUORIDE.  —  BORIC   ACID.  193 

Properties.  —  In  a  state  of  purity,  boron  chloride  is  a  color- 
less, mobile,  and  highly-refractive  liquid,  boiling  at  17°.  It 
fumes  in  the  air,  and  is  readily  decomposed  by  water  into  boric 
and  hydrochloric  acids. 

BoCP  -f  3H20  =  3HC1  +  Bo(OH)3 

BORON   FLUORIDE. 

BoFl» 

Density  compared  to  air     ........       2.31 

Density  compared  to  hydrogen     ......     34. 

Preparation.  —  Boron  fluoride  was  discovered  by  Gay-Lussac 
and  Thenard  in  1810.  It  is  prepared  by  heating  in  a  glass 
retort  an  intimate  mixture  of  one  part  of  boric  oxide  and  two 
parts  of  powdered  calcium  fluoride  with  twelve  parts  of  sul- 
phuric acid.  The  gas  disengaged  is  collected  over  mercury. 

3CaFP  +  Bo203  +  3H2SO*  =  3CaS04  +  3H20  +  2BoFP 

Calcium  Boric  oxide.  Calcium  sulphate. 

fluoride. 

Properties.  —  Boron  fluoride  is  a  colorless  gas,  having  a  suf- 
focating odor.  It  produces  abundant  fumes  in  the  air,  and  is 
very  soluble  in  water,  which  dissolves  about  800  times  its 
volume  of  this  gas.  Its  affinity  for  water  is  so  great  that  it 
carbonizes  paper  and  analogous  organic  substances,  from  which 
it  removes  the  elements  of  water. 

The  solution  of  boron  fluoride  in  water  is  accompanied  by  a 
chemical  reaction  ;  when  the  aqueous  solution  of  this  gas,  satu- 
rated at  the  ordinary  temperature,  is  cooled  to  0°,  crystals  of 
boric  acid  are  deposited,  and  a  very  acid  liquid  is  obtained, 
known  as  hydrofluoboric  acid  ;  its  composition  is  expressed  by 
the  formula  : 

BoFl4H  =  BoFP.HFl 

BORIC   ACID. 


Preparation.  —  Boric  acid  was  discovered  by  Homberg  in 
1702.  It  is  found  in  the  free  state  in  the  craters  of  certain 
volcanoes,  and  exists  in  solution  in  the  lagoni  of  Monte- 
Rotondo,  in  Tuscany.  These  are  muddy  little  lakes,  through 
which  arise  the  gaseous  emanations  from  the  fissures  of  a  vol- 
canic soil.  The  gases  (suffioni)  contain  sensible  traces  of  boric 
i  17 


194  ELEMENTS    OF    MODERN    CHEMISTRY. 

acid,  which  is  dissolved  by  the  water  of  the  lagoni.  On  evap- 
oration, this  water  furnishes  the  crude  boric  acid. 

Large  quantities  of  borax  (sodium  borate)  are  obtained  from 
Borax  Lake  and  from  Lake  Clear,  about  two  hundred  and  fifty 
miles  north  of  San  Francisco,  California.  The  crude  borax  is 
extracted  from  a  muddy  deposit,  which  is  obtained  from  the 
bottom  of  the  lakes  by  dredging. 

In  the  laboratory,  boric  acid  is  prepared  by  decomposing  a 
boiling  saturated  solution  of  borax  or  sodium  borate  with  dilute 
sulphuric  acid.  The  latter  is  added  in  small  portions  until 
the  liquid  strongly  reddens  litmus-paper ;  the  solution  is  then 
allowed  to  cool,  and  the  boric  acid  separates  in  the  crystalline 
form. 

Properties. — Pure  boric  acid  crystallizes  in  pearly  scales, 
somewhat  greasy  to  the  touch.  It  dissolves  in  25  parts  of 
water  at  18°,  and  is  much  more  soluble  in  boiling  water.  The 
solution  is  feebly  acid,  and  changes  blue  litmus  solution  to  a 
wine  color.  Boric  acid  dissolves  in  alcohol,  and  the  solution 
burns  with  a  green  flame. 

When  boric  acid  is  heated  in  a  platinum  crucible  to  a  tem- 
perature near  redness,  it  loses  all  of  its  water,  melts,  and  solidi- 
fies to  a  transparent  glass  on  cooling.  This  is  boric  oxide. 

2H3Bo03  =  Bo203  -f  3H20 

At  a  red  heat  this  body  dissolves  a  great  number  of  solid  sub- 
stances, particularly  the  metallic  oxides ;  it  then  yields  variously 
colored  glasses  on  cooling.  • 

Boric  oxide  is  not  decomposed  by  charcoal  at  a  red  heat,  but 
if  a  current  of  chlorine  be  passed  over  an  intimate  mixture  of 
boric  oxide  and  charcoal,  heated  to  bright  redness  in  a  porce- 
lain tube,  boron  chloride  and  carbon  monoxide  are  formed 
(Dumas). 

Bo203  +  3C  -f  3C12  =  2BoCP  -j-  SCO 


SILICON. 

Si  =  28 

Like  boron,  silicon  exists  amorphous  and  in  the- crystalline 
form.     It  was  discovered  by  Berzelius  in  1825. 

Preparation.     1.  Amorphous  Silicon. — Well-dried  sodium 


SILICON.  195 

fluosilicate  is  heated  with  half  its  weight  of  metallic  sodium : 
sodium  fluoride  is  formed  and  silicon  is  set  free. 

Na2FP.SiFl4    +    2Na2    ==    6NaFl    +    Si 

Sodium  fluosilicate.  Sodium  fluoride. 

On  cooling,  the  mass  is  exhausted,  first  with  cold,  and  after- 
wards with  hot,  water ;  a  brown  powder  of  amorphous  silicon 
remains. 

2.  Crystallized  Silicon. — Deville  and  Caron  obtained  crys- 
tallized silicon  by  projecting  a  mixture  of  3  parts  of  potassium 
and  silicon  double  fluoride,  4  parts  of  zinc,  and  1  part  of 
sodium  into  a  red-hot  crucible.  Fluoride  of  sodium  is  formed, 
and  the  silicon  set  free  dissolves  in  the  zinc  and  separates  in 
the  crystalline  form  on  cooling;  it  is  isolated  from  the  zinc 
by  dissolving  the  button  in  hydrochloric  acid ;  the  silicon 
remains  in  the  form  of  brilliant  laminae  or  needles.  These 
crystals  are  of  a  dark  steel-gray  color,  and  possess  a  metallic 
lustre;  they  are  composed  of  chaplets  of  regular  octahedra. 

Properties. — Amorphous  silicon  is  a  brown  powder,  more 
dense  than  water,  in  which  it  is  insoluble,  and  producing  dark 
stains  on  the  fingers.  When  heated  in  the  air.  it  takes  fire  and 
burns  with  a  bright  light  into  silicic  oxide,  SiO2. 

Crystallized  silicon  has  a  density  of  2.49.  It  may  be  heated 
to  redness  in  oxygen  without  taking  fire,  but  when  it  is  calcined 
with  potassium  carbonate  the  latter  is  decomposed  with  a  vivid 
emission  of  light,  potassium  silicate  being  formed  and  carbon 
being  set  free.  Crystallized  silicon  resists  the  oxidizing  action 
of  both  potassium  nitrate  and  potassium  chlorate,  but  it  dis- 
solves slowly  in  a  boiling  solution  of  potassium  hydrate,  hydro- 
gen being  disengaged  and  potassium  silicate  being  formed.  It 
burns  when  heated  to  redness  in  an  atmosphere  of  chlorine, 
silicon  chloride  being  formed. 

HYDROGEN  SILICIDE. 

Probable  formula  SiH* 

Preparation. — This  compound  was  discovered  by  Wohler 
and  Buff  in  1857.  Magnesium  silicide*  is  introduced  into  a 
two-necked  bottle,  which  is  then  entirely  filled  with  water  that 

*  Wohler  prepares  this  silicide  by  fusing  in  a  crucible  a  mixture  of  40 
parts  of  magnesium  chloride,  35  parts  of  silicon  and  sodium  double  fluor- 
ide, and  10  parts  of  sodium  chloride,  these  salts  being  previously  mixed 
with  10  parts  of  sodium  in  minute  frngraents. 


196  ELEMENTS    OF    MODERN   CHEMISTRY. 

has  been  recently  boiled.  One  of  the  necks  of  the  bottle  is 
fitted  with  a  funnel-tube  which  passes  to  the  bottom  of  the 
bottle,  while  to  the  other  is  adapted  a  delivery-tube  leading  to 
the  pneumatic  trough  ;  this  tube  also  should  be  completely  filled 
with  water  so  that  there  is  not  a  single  bubble  of  air  in  the 
whole  apparatus.  Concentrated  hydrochloric  acid  is  then 
introduced  by  the  funnel-tube,  and  immediately  reacts  with 
the  magnesium  silicide,  forming  magnesium  chloride,  which 
dissolves,  and  hydrogen  silicide,  which  is  disengaged  and  must 
be  collected  in  jars  filled  with  recently  boiled  water. 

Properties.  —  The  gas  thus  obtained  is  not  pure  hydrogen 
silicide  ;  it  contains  an  excess  of  hydrogen.  It  is  colorless  and 
insoluble  in  water  from  which  the  air  has  been  expelled. 
Water  containing  air  in  solution  oxidizes  it. 

If  bubbles  of  the  gas  be  allowed  to  escape  through  the  water 
of  the  trough,  each  bubble  takes  fire  on  coming  to  the  surface, 
burning  with  a  bright  light  and  a  little  explosion,  and  producing 
a  white  smoke  of  silicic  oxide.  This  smoke  forms  rings  like 
those  produced  by  hydrogen  phosphide  under  the  same  circum- 
stances, but  often  colored  brown  %by  a  portion  of  silicon  set  free. 

The  incomplete  combustion  of  hydrogen  silicide  is  accompa- 
nied by  a  brown  deposit  of  amorphous  silicon.  At  a  red  heat, 
hydrogen  silicide  is  decomposed  into  hydrogen  and  silicon. 

SILICON   CHLORIDE. 

SiCl* 

This  compound  is  formed  when  silicon  is  heated  to  dull 
redness  in  a  current  of  chlorine,  or  when  a  current  of  the 
latter  gas  is  passed  over  an  incandescent  mixture  of  charcoal 
and  silica. 


+     C2     -J-     Cl4     =     SiCl4     +     2CO 

Silicic  oxide.  Carbon  monoxide. 

Preparation.  —  Precipitated  silica,  lamp-black,  and  oil  are 
intimately  mixed  into  a  stiff  paste.  This  paste  is  made  into 
little  balls,  which  are  put  into  a  crucible,  the  cover  of  which  is 
then  luted  on,  and  the  whole  is  heated  to  redness  in  a  furnace. 
When  cool,  the  balls  are  introduced  into  a  porcelain  tube  or  a 
clay  retort  (Fig.  74),  which  is  then  heated  to  bright  redness, 
while  a  current  of  carefully-dried  chlorine  is  passed  through. 
The  silicon  chloride  and  the  carbon  monoxide  formed  are 


SILICON   FLUORIDE. 


197 


passed  through  two  U  tubes  surrounded  by  a  mixture  of  ice 
and  salt.  The  silicon  chloride  is  thus  condensed. 

Properties. — Silicon  chloride  is  a  volatile,  colorless  liquid, 
of  an  irritating  odor.  It  fumes  in  the  air.  Its  density  is  1.52, 
and  it  boils  at  59°. 

It  is  instantly  decomposed  by  water,  silicic  and  hydrochloric 
acids  being  formed.  A  part  of  the  silicic  acid  is  precipitated 


FIG.  74. 

in  the  form  of  a  jelly,  while  another  part  remains  in  solution. 

The  latter  is  perhaps  a  hydrate  corresponding  to  the  chloride. 

SiCl4  +  4H20  =  4HC1  -f  Si(OH)4 

There  exists  a  tetrabromide  of  silicon,  SiBr4,  and  a  tetra- 
iodide,  SiP,  both  corresponding  to  the  chloride  which  has  just 
been  described. 

Friedel  has  recently  discovered  an  iodide,  Si2!6,  remarkable 
as  belonging  to  an  entirely  new  series. 

SILICON    FLUORIDE. 

SiFl* 

Density  compared  to  air 3.6 

Density  compared  to  hydrogen 52. 

Preparation. — An  intimate  mixture  of  silicious  sand  and 
17* 


198  ELEMENTS   OF   MODERN   CHEMISTRY. 

finely-powdered  calcium  fluoride,  or  fluor  spar,  is  introduced 
into  a  glass  flask  (Fig.  75),  and  a  sufficient  quantity  of  sul- 
phuric acid  is  added  to  reduce  the  whole  to  a  creamy  consistence. 
A  gentle  heat  is  applied,  and  the  gas  disengaged  may  be  col- 
lected over  mercury. 

2CaFl2  -f  2H2SO*  -f  SiO2  =  2CaSO  -f  SiFl*  +  2H20 

Calcium  fluoride.  Silicic  oxide.  Calcium  sulphate. 


FIG.  75. 

Properties. — Silicon  fluoride  is  a  colorless,  suffocating  gas, 
producing  white  fumes  when  allowed  to  escape  into  the  air.  It 
may  be  liquefied  by  a  low  temperature  and  a  strong  pressure. 
On  contact  with  water  it  is  decomposed,  silicic  hydrate  separat- 
ing in  gelatinous  flakes,  and  hydrofluosilicic  acid  being  formed. 
3SiFl4  +  3H20  =  2(H2Fl2.SiFl4)  -f  H'SiO8 

Hydrofluosilicic  acid. 

Hydrofluosilicic  Acid. — A  saturated,  aqueous  solution  of 
this  acid  is  a  highly  acid  liquid,  fuming  in  the  air,  and  evapo- 
rating slowly  at  40°  from  a  platinum-dish  without  leaving  any 
residue. 

It  is  prepared  by  passing  gaseous  silicon  fluoride  into  water 
under  which  is  a  layer  of  mercury.  The  delivery-tube  must 
dip  beneath  the  surface  of  the  mercury,  so  that  the  silicon  flu- 
oride can  only  come  in  contact  with  the  water  after  passing 
through  the  metal ;  otherwise  the  delivery-tube  would  become 
obstructed  by  the  deposit  of  gelatinous  silica. 

Hydrofluosilicic  acid  is  employed  as  a  reagent  in  the  labora- 
tory. It  precipitates  the  salts  of  potassium  and  sodium,  form- 
ing insoluble  fluosilicates,  R2Fl2.SiFl*. 


SILICIC   OXIDE   AND    ACIDS.  199 


SILICIC   OXIDE   AND  ACIDS. 

(SILICA.) 

Native  State. — Silicic  oxide  is  widely  diffused  in  nature. 
It  occurs  crystallized,  as  the  different  varieties  of  quartz ;  amor- 
phous, as  agate,  chalcedony,  cornelian,  flint,  etc. ;  granulated,  it 
is  found  in  sandstones  and  the  sand  produced  by  their  disaggre- 
gation ;  in  this  case  it  is  often  mixed  with  variable  quantities 
of  alumina  and  oxide  of  iron. 

Rock-crystal  is  pure  silicic  oxide.  It  occurs  as  six-sided 
prisms,  terminated  by  pyramids  of  six  faces  (Fig.  *76). 

As  hydrate,  silica  exists  in  various  minerals,  such 
as  opal  and  hydrophane.  It  is  also  found  in  the 
form  of  pulverulent  deposits  and  in  solution  in 
many  running  waters,  in  large  proportion  in  the 
hot  waters  of  the  geysers  in  Iceland. 

Properties. — Quartz  is  infusible  at  the  highest 
furnace  heats,  but  undergoes  a  viscous  fusion  when 
introduced  into  the  flame  of  the  oxyhydrogen  blow- 
pipe. Neither  carbon  nor  potassium  is  capable  of 
reducing  it,  even  at  the  highest  temperatures.  It 
is  not  attacked  by  acids,  with  the  exception  of  hydrofluoric 
acid.  Boiling  alkaline  solutions  scarcely  affect  it,  but  the  amor- 
phous varieties  of  silica,  such  as  flint,  as  well  as  opal  and  the 
other  hydrates,  dissolve  more  readily  in  boiling  solutions  of  the 
alkaline  hydrates. 

All  of  the  varieties  of  silica,  when  heated  to  redness  with 
the  alkalies  or  alkaline  carbonates,  combine  with  the  bases, 
forming  silicates  which  enter  into  fusion  at  a  high  temperature 
and  solidify  to  a  vitreous  mass  on  cooling.  Potassium  silicate, 
or  soluble  glass,  is  a  transparent  mass,  soluble  in  water.  When 
hydrochloric  acid  is  added  to  this  solution,  potassium  chloride 
is  formed  and  silicic  acid  is  precipitated  as  a  gelatinous  mass, 
which  is  not  insoluble  in  water.  An  aqueous  solution  of  silicic 
acid  may  be  obtained. 

If  hydrochloric  acid  be  added  to  a  dilute  solution  of  potas- 
sium silicate,  the  liquid  remains  transparent  although  it  contains 
silicic  acid.  It  may  be  poured  into  a  dialyser,  composed  of  a 
piece  of  parchment-paper  stretched  over  a  wooden  or  glass  ring, 
and  floated  on  the  surface  of  pure  water  contained  in  another 
vessel.  The  potassium  chloride  gradually  passes  through  the 


200  ELEMENTS    OF    MODERN    CHEMISTRY. 

membrane,  as  would  any  crystallizable  body,  and  the  silicic 
acid  remains  alone  dissolved  in  the  water  in  the  dialyser,  as 
all  other  amorphous  bodies  which  are  soluble  in  water  would 
do.  Graham  gave  the  name  dialysis  to  this  separation  of  crys- 
tallizable bodies,  which  he  named  crystalloids,  from  uncrystal- 
lizable  bodies,  which  he  named  colloids,  by  means  of  certain 
membranes.  The  former  bodies  pass  through  the  membranes, 
which  are,  however,  impermeable  to  the  colloids. 

The  silicic  acid  which  remains  in  solution  probably  consti- 
tutes normal  silicic  acid,  H4Si04  ==  SiO2  -f  2H20. 

This  hydrate  is  not  known  in  the  pure  state.  Ebelmen  has 
described  a  hydrate,  H2Si03,  which  may  be  considered  as  the 
first  hydrate  of  silicic  oxide. 

H4Si04  —  H20  =  H2Si03 
H4Si04  —  2H20  =  SiO2 

There  are  other  silicic  hydrates  having  more  complex  com- 
positions. 

Uses. — Silica  is  largely  employed  in  all  of  its  various  forms. 
Crystallized  quartz,  or  rock  crystal,  is  used  for  the  manufacture 
of  ornaments,  spectacle-glasses,  and  lenses.  Chalcedony,  onyx, 
and  opal  are  sought  for  by  the  lapidary  and  engraver.  Agate, 
which  is  very  hard,  is  used  for  the  manufacture  of  mortars,  etc. 
Sandstones  serve  for  building  purposes  and  for  grindstones; 
sand,  for  mortars  and  the  manufacture  of  glass  and  pottery. 


CARBON. 

0  =  12 

Natural  State  and  Varieties. — The  carbon  of  chemists  is 
pure  charcoal.  This  substance  is  known  to  all ;  black,  friable, 
light,  absolutely  fixed,  inalterable  by  the  air  at  ordinary  tem- 
peratures, but  combustible  when  heated  in  the  air,  it  results 
from  the  calcination  of  organic  matters,  and  particularly  wood, 
in  closed  vessels.  But  carbon  by  no  means  always  reveals 
these  same  properties.  It  occurs  in  nature  under  forms  so 
different  that  it  is  impossible  to  apply  a  general  description  to 
all  of  its  known  varieties.  What  could  be  more  different,  as 
far  as  physical  properties  are  concerned,  from  the  soot  deposited 
by  a  smoky  flame,  or  the  light,  porous,  and  opaque  charcoal, 
than  the  hard,  dense,  and  transparent  substance  found  in  nature 


CARBON.  201 

in  the  form  of  diamond  ?  Nevertheless,  these  bodies  are  com- 
posed of  one  and  the  same  substance,  carbon ;  alike,  they  all 
burn  in  oxygen  at  a  high  temperature,  producing  carbonic  acid 
gas. 

Among  the  various  forms  which  carbon  assumes,  and  which 
constitute  one  of  the  most  curious  examples  of  dimorphism,  the 
following  may  be  described : 

Diamond. — This  is  the  hardest  of  all  bodies ;  it  scratches  all 
others,  and  can  only  be  trimmed  by  grinding  with  its  own  dust. 

It  is  found  crystallized  in  the  form  of  the  regular  octahe- 
dron and  the  modifications  thereof,  among  which  must  be  men- 


FIG.  77. 

tioned  the  polyhedra  of  twenty-four  and  forty-eight  faces.    The 
faces  are  generally  convexly  curved  (Fig.  7f  )• 

The  density  of  the  diamond  is  between  3.50  and  3.55.  It  is 
a  bad  conductor  of  heat  and  electricity ;  it  strongly  refracts  and 
disperses  light.  From  this  latter  fact  Newton  first  divined  its 
combustible  nature,  which  was  proved,  in  1694,  by  the  Floren- 
tine academicians  of  del  Cimento,  who  burned  a  diamond  in  the 
focus  of  a  concave  mirror.  Lavoisier  and  Davy  repeated  this 
celebrated  experiment.  Exposed  to  the  high  temperature  of 
the  voltaic  arc  between  two  carbon  poles  in  a  vacuum,  the  dia- 
mond swells  up,  blackens,  and  is  converted  into  a  substance 
analogous  to  coke  ( Jacquelain). 

Graphite,  or  Plumbago. — This  is  a  crystalline  variety  of 
carbon,  which  is  found  in  primitive  rocks  in  brilliant  steel-gray 
foliated  masses.  It  sometimes  occurs  in  hexagonal  laminae. 
It  can  be  scratched  with  the  finger-nail,  and  leaves  a  black 
trace  when  drawn  over  paper.  Its  density  is  2.2,  and  it  con- 
ducts heat  and  electricity.  It  burns  only  at  very  high  tem- 
peratures; ordinarily,  it  contains  from  one  to  two  per  cent,  of 
foreign  matters, 
i* 


202  ELEMENTS    OP    MODERN    CHEMISTRY. 

It  has  been  obtained  artificially.  Melted  iron  possesses  the 
property  of  dissolving  carbon  at  a  very  high  temperature,  and 
again  depositing  it  on  cooling  in  the  form  of  hexagonal  scales 
of  graphite. 

Plumbago  is  used  for  the  manufacture  of  lead-pencils  and 
crucibles,  and  is  called  black  lead. 

There  are  other  natural  varieties  of  carbon,  but  they  are 
far  from  presenting  the  same  degree  of  purity  as  diamond  or 
graphite.  They  are: 

Anthracite,  a  hard  and  compact  variety  of  carbon  containing 
from  8  to  10  per  cent,  of  earthy  matters. 

Bituminous  coal,  a  brilliant,  black  variety,  strongly  impreg- 
nated with  bituminous  and  earthy  matters.  It  has  been  pro- 
duced by  the  slow  decomposition  of  vegetable  matters  buried 
in  the  earth  in  the  early  geological  ages.  This  origin  is  indi- 
cated by  the  impressions  of  leaves,  stems,  and  fruits,  which  are 
evident  in  certain  specimens  of  this  coal.  It  contains  only 
from  75  to  88  per  cent,  of  carbon.  When  it  is  calcined  in 
closed  vessels,  it  disengages  combustible  gases  and  products 
which  may  be  condensed  in  the  liquid  form  and  then  separate 
into  two  layers.  One  is  aqueous  and  ammoniacal,  while  the 
other  is  composed  of  tar.  The  residue  of  the  distillation  of 
bituminous  coal  is  coke.  The  interior  walls  of  the  cast-iron 
vessels  in  which  coal  is  distilled  become  covered  with  a  com- 
pact layer  of  a  gray,  dense,  hard  and  sonorous  carbon,  which 
is  a  good  conductor  of  heat  and  electricity.  This  is  the  carbon 
of  gas-retorts,  and  is  produced  by  the  igneous  decomposition 
of  hydrocarbons  rich  in  carbon,  which  are  disengaged  during 
the  calcination  of  the  coal. 

Fat  coals  are  those  which  burn  with  a  long  flame,  softening 
in  burning ;  dry  coals  burn  with  a  short  flame  which  produces 
less  heat  than  the  preceding. 

Lignite  is  a  combustible  mineral  containing  less  carbon,  and 
more  impure  than  bituminous  coal ;  it  is  found  in  the  lower 
tertiary  formations.  Natural  jet,  which  is  employed  for  the 
manufacture  of  ornaments,  is  a  variety  of  lignite. 

Among  the  artificial  carbons,  independently  of  coke,  may 
be  mentioned  wood  charcoal,  lamp-black,  and  animal  char- 
coal. 

Wood  Charcoal. — When  wood  is  calcined  in  closed  vessels 
it  leaves  a  residue  which  is  ordinary  charcoal.  It  is  prepared 
on  the  large  scale  by  two  processes,  carbonization  in  stacks, 


CARBON. 


203 


which  is  carried  on  in  the  forests,  and  distillation  in  closed 
vessels.  Charcoal  is  amorphous,  brittle,  and  sonorous,  a  bad 
conductor  of  heat  and  electricity.  Its  density  does  not  exceed 
1.57.  The  lighter  varieties  are  the  more  combustible.  Its 
combustion  leaves  a  residue  of  one  or  two  per  cent,  of  cinders, 
formed  principally  of  mineral  salts,  among  which  the  most 
abundant  are  the  carbonates  of  calcium  and  potassium. 


FIG.  78. 


Lamp-Hack  is  produced  by  the  incomplete  combustion  of 
organic  substances  rich  in  carbon.  When  rosin  or  tallow  is 
burned,  a  dense  smoke  is  produced  which  is  composed  of  par- 


204 


ELEMENTS    OF    MODERN    CHEMISTRY. 


tides  of  carbon  that  have  escaped  combustion.  In  the  arts, 
lamp-black  is  procured  by  burning  rosin  in  cast-iron  pots,  C 
(Fig.  78),  heated  by  a  fire,  F.  The  vapors  given  off'  are  ig- 
nited, and  the  smoke  is  conducted  into  a  chamber,  A,  the  walls 
of  which  are  hung  with  canvas.  On  this  the  lamp-black  is  de- 
posited, and  is  detached  by  lowering  the  cone  B,  which  acts  as 
a  scraper.  Lamp-black  is  not  pure  carbon.  It  contains  tarry 
and  oily  matters,  from  which  it  may  be  freed  by  calcination  in 
a  covered  crucible.  It  is  used  for  the  manufacture  of  printing- 
inks. 

Animal  charcoal  is  produced  by  calcining  animal  matters, 
such  as  blood,  the  debris  of  skin,  horn,  bone,  etc.,  in  closed 
vessels.  Bone-black  or  ivory-black  contains  the  calcareous 
salts,  calcium  phosphate  and  carbonate,  which  form  the  base 
of  the  osseous  tissue.  The  carbon  is  consequently  disseminated 
through  a  porous  mass.  These  salts  may  be  extracted  by 
treating  the  bone-black  with  dilute  hydrochloric  acid,  by  which 
they  are  dissolved.  The  residue,  washed  with  water  and  dried, 
is  known  as  washed  or  purified  animal  charcoal. 

Absorbent  Properties  of  Charcoal. — The  amorphous  and 
porous  varieties  of  carbon,  of  which  several  forms  have  been 
described,  possess  the  property  of  absorbing  and  retaining  in 
their  pores,  gases,  liquid  and  solid  bodies.  It  is  to  this  absorp- 
tive faculty  that  are  due  the  decolorizing  and  disinfecting 
properties  of  charcoal,  which  are  made  use  of  to  a  large  extent 
in  the  arts. 

If  a  piece  of  incandescent  charcoal  be  plunged  into  mercury 
that  it  may  cool  out  of  contact  with  the  air,  and  then  be  intro- 
duced into  a  small  jar  filled  with  ammonia  or  hydrochloric  acid 
over  the  mercury-trough,  the  gas  is  at  once  absorbed  and  the 
mercury  rises  in  the  jar. 

The  following  table,  by  Th.  de  Saussure,  indicates  the  quan- 
tities of  several  gases  which  are  absorbed  by  one  volume  of 
charcoal : 

1  volume  of  charcoal  absorbs  90  volumes  of  ammonia. 


85 

65 

55 

40 

35 
9.42 
9.25 
7.50 
1.75 


hydrochloric  acid, 
sulphurous  oxide, 
hydrogen  sulphide, 
nitrogen  monoxide, 
carbon  dioxide, 
carbon  monoxide, 
oxygen, 
nitrogen, 
hydrogen. 


CARBON. 


205 


Charcoal  increases  in  weight  when  exposed  to  the  air,  for 
it  absorbs  and  condenses  the  atmospheric  moisture.  When 
plunged  into  water  charged  with  a  small  quantity  of  hydrogen 
sulphide,  it  absorbs  that  gas  and  removes  the  odor  of  the  water. 
The  disinfecting  properties  of  charcoal  are  thus  easily  explained. 
It  is  well  known  that  charcoal  will  remove  the  unpleasant  odor 
of  corrupted  waters,  of  meats  slightly  spoiled,  and  in  general 
of  organic  matters  in  a  state  of  putrefaction.  A  layer  of  char- 
coal between  two  layers  of  sand  is  an  excellent  filter  for  the 
clarification  of  drinking  waters. 

The  decolorizing  properties  of  charcoal  are  another  mani- 
festation of  this  general  faculty  of  absorption,  which  is  pos- 
sessed in  the  highest  degree  by  animal  charcoal.  If  litmus 
solution  or  red  wine  be  agitated  with  a  sufficient  quantity  of 
animal  charcoal  and  subsequently  filtered,  the  liquids  pass 
through  colorless. 


FIG.  70. 

This  property  of  animal  charcoal  is  largely  applied  in  the 
arts,  particularly  for  decolorizing  sugars  and  syrups. 

Chemical  Properties.  —  Carbon  is  distinguished  by  its 
powerful  affinity  for  oxygen,  an  affinity  which  is  not,  however, 

18 


206  ELEMENTS   OF   MODERN   CHEMISTRY. 

exercised  except  at  high  temperatures.  It  only  combines  with 
oxygen  at  a  red  heat,  and  remains  incandescent  as  long  as  com- 
bination goes  on,  the  heat  produced  by  the  combination  being 
sufficient  to  maintain  the  incandescence.  In  pure  oxygen  it 
burns  with  a  brilliant  light.  The  product  of  the  combustion 
is  carbonic  acid  gas. 

By  the  aid  of  heat,  carbon  decomposes  a  great  number  of 
oxygenized  compounds,  removing  and  combining  with  the 
whole  or  a  part  of  their  oxygen.  This  decomposition  takes 
place  at  comparatively  low  temperatures  when  the  oxygenized 
body  does  not  strongly  retain  its  oxygen ;  in  this  case,  carbon 
dioxide  is  formed,  and  the  reduction  of  cupric  oxide  by  char- 
coal furnishes  an  example.  In  the  contrary  case,  the  reduction, 
that  is,  the  decomposition  of  the  oxidized  body,  requires  a  very 
high  temperature ;  carbon  monoxide  is  then  formed.  The  re- 
duction of  zinc  oxide  by  charcoal  is  an  example. 

If  an  incandescent  charcoal  be  rapidly  plunged  under  a  bell- 
jar  filled  with  water  on  the  pneumatic  trough,  bubbles  of  gas 
arise  and  collect  in  the  jar  (Fig.  79).  They  are  formed  of  a 
mixture  of  hydrogen,  carbon  monoxide,  and  a  small  quantity 
of  carbon  dioxide.  These  gases  are  produced  by  the  decom- 
position of  the  water  by  the  charcoal,  which  was  red-hot  at  the 
moment  of  contact  with  the  liquid. 

C  -f  H20  =  H2  -f  CO  carbon  monoxide. 

Carbon  combines  directly  with  sulphur  at  a  high  tempera- 
ture, forming  carbon  disulphide. 


COMPOUNDS   OF   CARBON  AND  OXYGEN. 

Two  compounds  of  carbon  and  oxygen  are  known : 

Carbon  monoxide .     .     CO 

Carbon  dioxide,  or  carbonic  acid  gas CO2 

The  latter  body,  which  has  long  been  known  as  carbonb 
acid,  is  the  oxide  corresponding  to  the  true  carbonic  acid, 
which  would  be 

CO2  +  H20  =  H2C03 

This  normal  carbonic  acid  is  as  yet  unknown  :  it  is  doubtless 
too  unstable  to  exist  in  the  free  state.  However,  its  existence 


CARBON    MONOXIDE. 


207 


may  be  admitted,  for  a  corresponding  compound  is  known  in 
sulphocarbonic  acid  H2CS3. 


CARBON   MONOXIDE. 

Density  compared  to  air 0.967 

Density  compared  to  hydrogen 14. 

Molecular  weight  CO =28. 

Preparation. — 1.  An  intimate  mixture  of  zinc  oxide  and 
charcoal  may  be  calcined  in  a  clay  retort. 

ZnO  +  C  =  CO  +  Zn 

2.  A  convenient  method  of  preparing  carbon  monoxide  con- 
sists in  heating  oxalic  acid  with  an  excess  of  sulphuric  acid  in 
a  glass  flask.  The  oxalic  acid  loses  the  elements  of  water, 
which  it  yields  to  the  sulphuric  acid,  and  breaks  up  into  carbon 
dioxide  and  carbon  monoxide. 


C2H20*    =    CO      4-      CO2    + 

Oxalic  acid.    Carbon  monoxide.  Carbon  dioxide. 


H2O 


FIG.  80. 

The  mixture  of  the  two  gases  is  passed  through  a  wash-bottle, 
B  (Fig.  80)",  containing  a  solution  of  potassium  hydrate,  by 


208  ELEMENTS    OF    MODERN    CHEMISTRY. 

which  the  carbon  dioxide  is  absorbed,  potassium  carbonate  being 
formed.  Carbon  monoxide  alone  passes  through,  and  may  be 
collected  over  water. 

Properties. — Carbon  monoxide  is  a  colorless,  odorless  gas. 
It  is  neutral,  and  does  not  trouble  lime-water,  which  distin- 
guishes it  from  carbon  dioxide.  It  extinguishes  burning  bodies, 
but  is  combustible  itself,  burning  in  the  air  with  a  blue  flame, 
and  forming  carbon  dioxide.  It  is  not  only  unfit  for  respira- 
tion, but  is  very  poisonous. 

Composition. — If  two  volumes  of  carbon  monoxide  be 
mixed  with  one  volume  of  oxygen  in  an  eudiometer,  and  a 
spark  be  passed,  complete  combustion  takes  place,  and  the 
three  volumes  of  the  primitive  mixture  are  reduced  to  two 
volumes  of  carbon  dioxide.  This  can  be  verified  by  passing 
into  the  eudiometer  a  solution  of  potassium  hydrate,  which  will 
completely  absorb  the  new  gas. 

It  hence  follows  that  two  volumes  of  carbon  monoxide  con- 
tain the  same  quantity  of  carbon  as  two  volumes  of  carbon 
dioxide.  Knowing  from  other  circumstances  that  two  volumes 
of  carbon  dioxide  contain  two  volumes  of  oxygen,  it  follows 
that  two  volumes  of  carbon  monoxide  contain  one  volume  of 
oxygen.  Its  composition  is  then  expressed  by  the  formula 
CO  —  2  volumes. 

Carbon  monoxide  undergoes  dissociation  at  a  very  high  tem- 
perature. By  operating  under  special  conditions,  H.  Sainte- 
Claire  Deville  has  succeeded  in  resolving  it  into  carbon  and 
oxygen. 

It  is  almost  insoluble  in  water,  but  is  absorbed  by  a  solution 
of  cuprous  chloride  in  hydrochloric  acid  (Doyere  and  F.  Le 
Blanc).  Advantage  is  taken  of  this  property  in  volumetric 
analysis  to  separate  carbon  monoxide  from  certain  other  gases. 

When  heated  for  a  long  time  to  100°,  in  sealed  tubes  with 
potassium  hydrate,  it  combines  with  the  alkali,  forming  potas- 
sium formate  (Berthelot). 

CO     -|-     KOH      =    KCHO2 

Potassium  hydrate.    Potassium  formate. 

It  is  a  beautiful  synthesis  of  formic  acid,  so  named  because  it 
exists  in  ants. 

Action  of  Chlorine  upon  Carbon  Monoxide. — Under  the 
influence  of  sunlight,  carbon  monoxide  combines  directly  with 
chlorine,  forming  a  gas  which  is  known  as  chloro-carbonic  oxide, 


CARBON    DIOXIDE.  209 

or  carbonyl  chloride.  It  was  formerly  called  phosgene  gas. 
One  volume  of  carbon  monoxide  combines  with  one  volume  of 
chlorine  to  form  one  volume  of  carbonyl  chloride,  so  that  the 
density  of  the  latter  is  equal  to  the  sum  of  the  densities  of 
carbon  monoxide  and  chlorine. 

Compared  to  Hydrogen.     Compared  to  Air. 
Density  of  carbon  monoxide  .     .     14.  0.967 

Density  of  chlorine 35.5  2.44_ 

Density  of  carbonyl  chloride      .     49.5  8.407 

At  ordinary  temperatures,  carbonyl  chloride  is  a  colorless 
gas,  having  a  suffocating  odor  that  provokes  tears.  At  a  low 
temperature,  it  condenses  to  a  colorless  liquid,  boiling  at  8.2° 
(Emmerling  and  Lengyel).  It  is  instantly  decomposed  by  water, 
with  the  formation  of  carbon  dioxide  and  hydrochloric  acid. 

COOP  +  H20  =  2HC1  +  CO2 

Its  mode  of  formation,  its  composition,  and  its  properties 
indicate  its  relations  to  carbon  dioxide. 

2  volumes  CO  absorb  2  volumes  of  chlorine  to  form  2  volumes  CO.C12 
2  volumes  CO  absorb  1  volume  of  oxygen  to  form  2  volumes  CO.O 

It  is  seen  that  carbon  monoxide  plays  to  a  certain  extent  the 
part  of  a  radical ;  it  combines  directly  with  oxygen  or  with 
chlorine  to  form  either  oxide  or  chloride  of  carbonyl.  It 
is  seen  also  that  carbonyl  chloride  represents  carbon  dioxide  in 
which  one  atom  of  oxygen  is  replaced  by  two  atoms  of  chlorine. 


CARBON  DIOXIDE. 

Density  compared  to  air 1.529 

Density  compared  to  hydrogen 22. 

Molecular  weight  CO2 =44. 

This  gas  was  discovered  by  Black  in  1648,  and  its  composi- 
tion was  recognized  by  Lavoisier  in  1776.  It  is  one  of  the 
constituents  of  the  atmosphere,  and  is  the  product  of  a  great 
number  of  reactions  which  take  place  on  the  earth's  surface, 
such  as  the  combustion  of  carbon  and  organic  matters,  respira- 
tion, and  the  phenomena  of  putrefaction  and  fermentation.  It 
issues  from  the  soil  of  volcanic  countries. 

18* 


210 


ELEMENTS   OF    MODERN    CHEMISTRY. 


Preparation. — Fragments  of  marble,  which  is  calcium  car- 
bonate, are  intro- 
duced into  a  two- 
necked  bottle  fitted 
with  a  delivery- 
tube  and  a  safety- 
tube  (Fig.  81). 
The  bottle  is  half- 
filled  with  water, 
and  hydrochloric 
acid  is  gradually 
added  by  the  fun- 
nel-tube. An  ef- 
fervescence imme- 
diately takes  place, 
due  to  the  disen- 
gagement of  car- 
bon dioxide. 
CaCP  -f  H20 


FIG.  81. 


CO2 


CaCO3       -f  2HC1  == 

Calcium  carbonate.  Calcium  chloride. 

The  gas  is  most  conveniently  collected  by  dry  downward 
displacement,  like  chlorine. 

Composition. — 1.  If  carbon  be  burned  in  oxygen,  the  latter 
is  converted  into  carbon  dioxide  without  changing  its  volume. 
Hence  two  volumes  of  carbon  dioxide  contain  two  volumes  of 
oxygen.  These  two  volumes  of  oxygen,  which  represent  two 
atoms,  are  combined  with  one  atom  of  carbon,  and  the  compo- 
sition of  a  molecule  of  carbon  dioxide  is  hence  expressed  by 
the  formula 

CO2  ==  2  volumes. 

2.  Dumas  and  Stas  determined  the  centesimal  composition 
of  carbon  dioxide  by  burning  a  known  weight  of  diamond  in 
oxygen,  and  carefully  weighing  the  carbon  dioxide  produced. 
By  subtracting  the  weight  of  the  diamond  burned  from  that  of 
the  carbon  dioxide,  the  weight  of  the  oxygen  was  determined. 
The  apparatus  employed  is  represented  in  Fig.  82. 

The  increase  in  weight  of  the  tubes  L,  M,  N,  0,  P  indicates 
the  quantity  of  carbon  dioxide  formed. 

Dumas  and  Stas  thus  found  that  100  parts  of  carbon  dioxide 
contain 

Carbon 27.27 

Oxygen 72.73 

100.00 


CARBON    DIOXIDE. 


211 


212 


ELEMENTS    OF    MODERN    CHEMISTRY. 


a  centesimal  relation  which  is  expressed  more  simply  by  the 
numbers 

Carbon 12 

Oxygen .     32 

44 

12  being  the  weight  of  one  atom  of  carbon,  and  32  the  weight 
of  two  atoms  of  oxygen. 

Physical  Properties. — Carbon  dioxide  is  colorless ;  it  has  a 
feeble,  somewhat  pungent  odor.  A  litre  of  this  gas  at  0°,  and 
under  the  pressure  of  760  millimetres,  weighs  1.966  grammes. 


FIG.  83. 

It  is  not  permanent.  Faraday  succeeded  in  liquefying  it  at 
a  temperature  of  0°,  under  a  pressure  of  36  atmospheres.  The 
apparatus  which  is  now  used  for  its  liquefaction  is  represented 
in  Fig.  83.  It  is  composed  of  two  reservoirs,  A  and  B,  com- 


CARBON    DIOXIDE.  213 

municating  by  the  metallic  tube  ?",  furnished  with  a  stop-cock 
at  each  end.  The  cylinders  are  made  of  heavy  cast-iron,  and 
are  further  strengthened  by  forged  iron  bands  forced  over 
their  circumference.  Each  cylinder  is  movable  on  a  horizon- 
tal axis,  h.  B  is  the  generator;  into  it  are  introduced  1800 
grammes  of  sodium  dicarbonate,  and  a  cylindrical  copper  tube, 
D,  containing  1000  grammes  of  ordinary  sulphuric  acid.  The 
cylinder  is  then  closed  by  a  strong  screw  plug,  and  a  few  oscil- 
lating movements  are  given  to  it  in  order  that  the  sulphuric 
acid  may  gradually  run  out  upon  the  sodium  dicarbonate. 
Carbon  dioxide  is  disengaged  and  is  liquefied  by  its  own  press- 
ure as  it  accumulates  in  the  apparatus.  By  the  effect  of  the 
chemical  action  the  temperature  is  raised  to  30  or  40°,  and, 
communication  being  established  between  the  two  cylinders, 
the  carbon  dioxide  distils  rapidly  into  the  receiver,  the  tem- 
perature of  which  is  about  15°. 

The  operation  is  repeated  several  times,  that  one  or  two  kilo- 
grammes of  the  liquid  may  accumulate  in  the  receiver.  A 
tube  passes  to  the  bottom  of  this  vessel,  and  on  opening  the 
stop-cock  which  closes  the  superior  extremity  of  this  tube,  a 
jet  of  the  liquid  is  thrown  out  with 
force ;  it  is  received  tangently  in  a 
metallic  box,  A,  A'  (Fig.  84),  having 
very  thin  sides.  In  this  a  portion 
of  the  oxide  solidifies  by  reason  of 
the  great  depression  of  temperature 
produced  by  the  change  of  another 
portion  into  the  gaseous  state.  A 
glittering-white,  flaky  mass  collects 
in  the  receiver,  having  the  appear- 
ance of  snow.  This  is  solid  carbon 
dioxide.  It  is  a  bad  conductor  of 
heat  and  electricity,  and  can  be  ex-  pIG  g4 

posed  to  the  air  for  a  few  minutes 

before  it  disappears.  In  reassuming  the  gaseous  form,  it  pro- 
duces an  intense  cold.  If  it  be  mixed  with  ether,  the  mixture, 
which  is  less  porous  and  a  better  conductor  of  heat,  can  produce 
a  lowering  of  temperature  as  great  as  — 90°.  By  pouring  it 
upon  mercury,  large  masses  of  that  metal  may  be  frozen. 

Drion  and  Loir  have  recently  succeeded  in  collecting  and 
maintaining  carbon  dioxide  in  the  liquid  state.  It  is  colorless 
and  mobile;  has  a  density  of  0.72  at  +27°,  and  0.98  at — 8°. 


214 


ELEMENTS    OF    MODERN    CHEMISTRY. 


This  considerable  difference  between  the  densities  is  due  to  the 
enormous  dilatation  which  the  liquid  undergoes  between  these 
limits  of  temperature.  Indeed,  ten  volumes  of  liquid  carbon 
dioxide  at  0°  occupy  fourteen  volumes  at  30°.  The  coefficient 
of  dilatation  of  the  liquid  is  then  superior  to  that  of  the  gas. 
Carbon  dioxide  is  incombustible,  and  extinguishes  burning 
bodies. 

If  carbon  dioxide  be  poured  from  one  vessel  into  another 
containing  a  lighted  candle,  it  falls  upon  the  flame  like  water, 

extinguishing  it  at  once  (Fig.  85). 
Lime-water  poured  into  a  jar 
of  carbon  dioxide  becomes  clouded, 
owing  to  the  formation  of  insolu- 
ble calcium  carbonate, 

These  experiments  permit  the 
easy  recognition  of  carbon  dioxide 
from  carbon  monoxide. 

Carbon  dioxide  dissolves  in  its 
own  volume  of  water  at  15°  under 
the  normal  pressure.  If  the  press- 
ure be  increased,  the  solubility  of 
the  gas  is  increased  in  the  same 
proportion.  Thus,  under  a  press- 
ure of  ten  atmospheres  one  litre 
of  water  will  dissolve  ten  litres  of 
carbon  dioxide  ;  but  it  must  be  remembered  that  under  a  press- 
ure of  ten  atmospheres  these  ten  litres  are  reduced  to  one  litre. 
Thus,  one  litre  of  water,  which  dissolves  one  litre  of  carbon 
dioxide  at  the  ordinary  pressure,  dissolves  also  one  litre  under 
a  pressure  of  ten  atmospheres,  and  it  may  be  said  that  water 
always  dissolves  its  own  volume  of  carbon  dioxide,  whatever 
may  be  the  pressure.  Water  saturated  with  carbon  dioxide 
under  strong  pressure,  disengages  a  portion  of  the  gas  as  soon 
as  the  pressure  is  removed.  Such  water  is  universally  known 
and  consumed  in  large  quantities  under  the  name  of  gaseous 
water  or  soda  water. 

The  solution  of  carbon  dioxide  exercises  a  much  more  ener- 
getic solvent  action  upon  certain  substances  than  pure  water. 
It  dissolves  calcium  carbonate,  forming  a  soluble  dicarbonate; 
it  is  even  capable  of  dissolving  calcium  phosphate,  transform- 
ing it  into  acid  phosphate,  which  is  soluble. 

Carbon  dioxide  is  more  soluble  in  alcohol  than  in  water. 


FIG.  85. 


CARBON   BISULPHIDE.  215 

It  is  undecomposable  by  heat  alone,  but  may  be  decomposed 
or  reduced  at  high  temperatures  by  contact  with  bodies  avid 
of  oxygen.  Such  substances  are  hydrogen  and  carbon.  With 
the  latter  body  the  reduction  takes  place  at  a  red  heat,  giving 
rise  to  the  formation  of  carbon  monoxide,  the  volume  of  which 
is  double  that  of  the  carbon  dioxide  employed. 

CO2         +         C  2CO 

Carbon  dioxide  (2  vols.).  Carbon  moaoxide  (4  vote.). 

CARBON  BISULPHIDE. 

CS2 

This  body  is  prepared  by  passing  sulphur  vapor  over  incan- 
descent charcoal.  In  the  arts,  the  operation  is  conducted  in 
cylindrical,  cast-iron  vessels,  filled  with  charcoal  and  heated  to 
redness,  into  which  sulphur  is  introduced.  The  carbon  disul- 
phide  distils,  and  is  condensed  in  a  suitable  cooling  apparatus. 

Carbon  disulphide  is  a  colorless,  very  mobile,  and  highly-re- 
fracting liquid.  Its  odor  is  strong  and  unpleasant.  Its  density 
at  15°  is  1.271,  and  it  boils  at  46°.  It  is  very  inflammable,  and 
burns  with  a  blue  flame,  producing  sulphurous  oxide  and  carbon 
dioxide. 

CS2  +  O6  =  2S02  +  CO2 

Its  vapor,  mixed  with  oxygen,  explodes  on  the  application 
of  flame. 

Carbon  disulphide  corresponds  in  composition  to  carbon 
dioxide. 

CO2  carbon  dioxide. 
CS2  carbon  disulphide. 

It  is  also  analogous  to  the  latter  body  in  its  chemical  func- 
tions. While  carbon  dioxide  combines  with  metallic  oxides, 
forming  carbonates,  carbon  disulphide  combines  with  metallic 
sulphides,  forming  sulphocarbonates. 

CO2     +     Na2O     =     Na2C03  corresponding  to  H2C03 

Sodium  oxide.    Sodium  carbonate.  Carbonic  acM 

(bypothetical). 

CS2  +    Na2S       =       Na2CS3  corresponding  to  H2CS3 

Sodium  sulphide.    Sodium  sulphocarbonate.  Sulphocarbonic  acid. 

Sodium  carbonate  and  sulphocarbonate  possess  the  same  con- 
stitution. By  the  action  of  strong  acids  they  should  give  anal- 
ogous products:  the  one,  carbonic  acid,  H2C03;  the  other, 


216  ELEMENTS   OF    MODERN    CHEMISTRY. 

sulphocarbonic  acid,  H2CS3.  The  latter  body  is  indeed  formed 
under  such  circumstances,  but  normal  carbonic  acid,  if  it  exist, 
possesses  no  stability,  and  at  once  decomposes  into  carbon  diox- 
ide and  water. 

H2C03  *=  CO2  +  H20 

Carbon  disulphide  is  employed  in  the  arts  in  the  manufac- 
ture of  vulcanized  caoutchouc,  and  as  a  solvent  for  caoutchouc 
in  the  fabrication  of  goods  impermeable  to  water  by  the  deposit 
of  a  thin  layer  of  that  substance.  It  is  also  employed  as  a 
solvent  for,  and  in  the  extraction  of,  fats  and  oils. 

CARBON  OXYSULPHIDE. 

Density  compared  to  air 2.1046 

Density  compared  to  hydrogen 30.4 

Molecular  weight  CSO =60. 

This  body  was  discovered  by  de  Than  in  1867.  It  is  inter- 
mediate between  carbon  dioxide  and  carbon  disulphide. 

COO  carbon  dioxide. 
CSO  carbon  oxysulphide. 
CSS  carbon  disulphide. 

Preparation. — It  is  prepared  by  decomposing  potassium  sul- 
phocyanide  by  dilute  sulphuric  acid.  Potassium  sulphate  and 
hydrosulphocyanic  acid  are  formed,  and,  in  the  presence  of  an 
excess  of  sulphuric  acid  and  water,  the  latter  decomposes  into 
ammonia  and  the  gas  carbon  oxysulphide  which  may  be  collected 
over  mercury;  the  ammonia  remains  combined  with  the  sul- 
phuric acid  in  the  form  of  sulphate. 

CSNH     +     H20     =     NH3     +      CSO 

Hydrosulphocyanic  acid  Carbon  oxysulphide. 

Properties. — Carbon  oxysulphide  is  a  colorless  gas,  having 
an  odor  like  that  of  carbon  disulphide,  but  also  recalling  that 
of  hydrogen  sulphide. 

On  contact  with  an  incandescent  body,  even  a  match  pre- 
senting a  spark  of  fire,  it  takes  fire,  burning  with  a  blue  flame, 
and  depositing  sulphur  if  the  supply  of  air  be  insufficient. 
With  one  and  a  half  times  its  volume  of  oxygen  it  constitutes 
an  explosive  mixture. 

2  volumes  of  carbon  oxysulphide      .     .  =  CSO  mixed  with 

3  volumes  of  oxygen  . =  O3  yield 

2  volumes  of  carbon  dioxide  .  =  CO2  and 

2  volumes  of  sulphur  dioxide  .     .     .     .  =  SO2 


COMPOUNDS    OP   CARBON    AND    HYDROGEN.  217 

Water  dissolves  about  its  own  volume  of  carbon  oxysulphide, 
but  the  solution  decomposes  in  a  few  hours,  with  the  formation 
of  hydrogen  sulphide  and  carbon  dioxide. 

CSO  +  H20  =  CO2  +  H2S 

Carbon  oxysulphide  is  absorbed  completely,  but  more  slowly 
than  carbon  dioxide,  by  solutions  of  the  alkaline  hydrates ;  by 
a  reaction  analogous  to  the  preceding,  a  sulphide  and  a  carbonate 
are  formed. 

COMPOUNDS   OF   CARBON   AND   HYDROGEN. 

These  compounds  are  numerous  and  important.  Carbon 
unites  with  hydrogen  in  different  proportions,  and  the  atoms  of 
carbon  and  hydrogen  may  accumulate  in  considerable  numbers 
in  the  molecules  of  their  compounds.  These  combinations  are 
called  hydrocarbons  or  carbides  of  hydrogen.  Hydrogen  mono- 
carbide,  or  marsh  gas,  contains  only  one  atom  of  carbon  com- 
bined with  four  atoms  of  hydrogen  ;  its  molecule  is  therefore 
represented  by  the  formula  CH*.  Tn  olefiant  gas,  or  ethylene, 
two  atoms  of  carbon  are  united  with  four  atoms  of  hydrogen ; 
in  the  volatile  liquid  known  as  benzine  or  benzol,  which  is  ob- 
tained in  large  quantities  from  coal-tar,  six  atoms  of  carbon  are 
combined  with  six  atoms  of  hydrogen.  Lastly,  the  molecule 
of  oil  of  turpentine  contains  ten  atoms  of  carbon  and  sixteen 
of  hydrogen. 

Hence  these  substances  give  us  the  following  formulae : 

CH4  methane,  or  marsh  gas. 
C2H*  ethylene,  or  olefiant  gas. 
C6H6  benzine. 
C10H16  turpentine. 

These  examples,  which  might  be  indefinitely  multiplied,  show : 
1st.  That  the  atoms  of  carbon  unite  in  various  proportions  with 
the  atoms  of  hydrogen  to  constitute  the  molecules  of  the  hydro- 
carbons. 2d.  That  they  accumulate  in  greater  or  less  numbers 
to  form  molecules  more  and  more  complex,  that  is,  containing 
an  increasing  number  of  atoms  of  carbon  and  hydrogen. 

All  of  these  bodies  must  be  considered  among  the  organic 
compounds ;  indeed,  the  latter  are  nothing  more  than  the  com- 
pounds of  carbon,  and  carbon  monoxide  and  dioxide  may  also 
be  properly  considered  as  the  most  simple  organic  combinations. 
K  19 


218 


ELEMENTS    OF    MODERN    CHEMISTRY. 


Hence  if  the  most  strictly  rigorous  method  were  adhered  to, 
the  description  of  the  compounds  of  carbon  and  oxygen  would 
be  followed  by  that  of  all  the  other  compounds  of  this  element, 
that  is,  of  all  the  organic  compounds.  However,  for  the  pur- 
poses of  study  it  is  advantageous  to  treat  the  latter  bodies 
separately,  and  they  will  be  so  considered  in  this  work.  The 
following  experiments  will  expose  some  of  the  general  proper- 
ties of  the  hydrocarbons  which  have  been  mentioned : 

1.  If  a  lighted  taper  be  applied  to  a  jar  of  methane,  which 
is  also  called  marsh  gas,  because  it  is  disengaged  from  the  muddy 
bottoms  of  marshes,  the  gas  takes  fire  and  burns  with  a  lumi- 
nous flame. 

2.  If  the  same  experiment  be  repeated  with  ethylene  gas, 
which  contains  for  the  same  proportion  of  hydrogen  twice  as 
much  carbon  as  marsh  gas,  a  still  more  luminous  flame  results. 

3.  It  is  well  known  that  benzine  and  turpentine  take  fire 
when  lighted,  and  burn  with  bright  flames ;  but  it  is  also  known 

that  their  flames  are  smoky. 

The  hydrocarbons  are  then 
combustible;  and  how  could 
they  be  otherwise,  since  they 
contain  only  two  combustible 
elements,  carbon  and  hydro- 
gen? The  products  of  the 
combustion  are  water  and 
carbon  dioxide,  and  the  forma- 
tion of  the  latter  gas  may  be 
proved  by  agitating  the  con- 
tents of  the  jars  in  which  the 
combustion  has  taken  place 
with  lime-water;  the  latter 
immediately  becomes  milky 
by  the  precipitation  of  calcium 
carbonate. 

This  combustion  is  more  or 
FIG.  86.  less  complete ;  when  the  gas  or 

vapor  which  burns  contains  a 

large  amount  of  combustible  elements,  the  oxygen  of  the  air 
may  not  be  present  in  sufficient  quantity  to  burn  them  all,  that 
is,  to  oxidize  them  completely.  Under  these  conditions  it  is 
the  hydrogen  which  is  burned  by  preference,  and  the  carbon 
partly  escapes  combustion. 


STRUCTURE    OF    FLAME. 


219 


A  flame  is  a  gas  or  vapor  in  combustion.  This  combustion 
is  an  oxidation,  and  it  is  the  oxygen  of  the  air  which  is  the 
agent.  In  order  that  it  may  take  place,  it  is  generally  neces- 
sary that  the  combustible  gas  shall  be  brought  to  a  high  tem- 
perature; but  once  commenced,  the  combustion  continues  of 
itself,  because  the  heat  disengaged  by 
the  oxidation  is  sufficient  to  maintain  the 
phenomenon.  But  if  a  flame  be  suddenly 
cooled,  the  combustion  is  at  once  arrested. 

A  flame  may  be  cooled  by  depressing 
into  it  a  piece  of  fine  wire  gauze.  The 
incandescent  gases  cannot  pass  through 
the  meshes  of  the  gauze  without  being 
cooled  by  contact  with  the  metal,  which 
is  a  good  conductor  of  heat.  For  this 
reason,  no  combustion  takes  place  above 
the  gauze  (Fig.  86). 

If  a  piece  of  wire  gauze  be  held  over 
an  escaping  jet  of  gas,  the  latter  may  be 
ignited  above  the  gauze,  and  will  burn 
without  the  combustion  being  propagated 
to  the  gas  below ;  the  gauze  acts  as  a 
screen,  separating  the  jet  into  two  portions, 
the  lower  cold  and  invisible,  the  upper  in 
combustion  and  luminous. 

Sir  Humphry  Davy  made  a  happy  ap- 
plication of  these  facts  in  the  construction 
of  the  miner's  safety-lamp.  This  is  an 
ordinary  lamp  surrounded  by  a  cylinder 
of  wire  gauze  (Fig.  87). 

Such  a  lamp  gives  less  light  than  one 
not  protected  by  an  envelope,  but  it  re- 
moves the  danger  of  explosions  of  fire- 
damp, for  when  an  explosive  mixture  is  plf,  §7 
formed  in  the  galleries  of  a  mine,  the  gas 
may  penetrate  to  the  interior  of  the  lamp  and  take  fire  there, 
but  the  flame  cannot  pass  through  the  cooling  envelope  of  wire 
gauze.  The  safety-lamps  are  now  constructed  with  the  lower 
part  of  the  cylinder  of  glass,  so  that  there  is  no  diminution  in 
the  amount  of  light  given. 

As  the  oxidation  of  combustible  elements  is  the  source  of 
heat,  it  is  evident  that  the  different  parts  of  a  flame  cannot  be 


220 


ELEMENTS    OF    MODERN    CHEMISTRY. 


uniformly  hot,  for  the  oxygen  of  the  surrounding  air  cannot 
equally  attain  all  portions.  The  exterior  borders  are  the  most 
intensely  heated;  they  are  surrounded  by  air,  and  constitute 
the  seat  of  combustion.  From  them  the  heat  is  radiated  not 
only  externally,  but  also  to  the  interior  of  the 
flame,  where  it  produces  interesting  phenomena. 
These  may  be  studied  by  analyzing  a  flame, 
that  is,  considering  separately  the  different  parts 
of  which  it  is  composed.  If  the  flame  of  a  can- 
dle be  examined,  it  will  be  found  to  present  three 
distinct  layers,  or  cones  (Fig.  88). 

1.  A  dark  central  part,  a,  which  surrounds 
*^e  wick-     This  is  known  as  the  obscure  cone, 
or  cone  of  generation;    its  temperature  is  not 
high. 

2.  A  luminous  part,  bbf,  surrounding  the  ob- 
scure cone.     This  is  the  centre  from  which  the 
light  is  emitted.     It  is  known  as  the  luminous 
cone,  or  cone  of  decomposition. 

3.  An  exterior  envelope,  cc',  thin,  and  pro- 
ducing but  little  light,  yellow  towards  the  sum- 
mit, 6j  and  bluish  towards  the  base,  dd'.    It  is  the 
cone  of  complete  combustion,  and  its  temperature 
is  the  highest. 

It  is  easy  to  account  for  these  phenomena. 
The  material  of  the  candle  is  melted  by  the  heat 

Fio.  88.  °f  tne  flame,  the  liquid  is  drawn  up  into  the 
wick  by  capillarity,  and  arrives  at  the  incan- 
descent summit.  There  it  is  decomposed,  producing  gases  and 
vapors  rich  in  carbon  and  hydrogen,  and  which  rise  around  the 
wick,  forming  an  irregular  cone.  The  gaseous  products  consti- 
tuting this  cone  do  not  present  the  same  composition  through- 
out. They  have  been  analyzed  by  H.  Sainte-Claire  Deville, 
by  the  aid  of  very  ingenious  processes. 

The  obscure  cone  is  formed  of  gaseous  products  holding  in 
suspension  finely-divided  carbon,  which  has  not  yet  arrived  at 
incandescence. 

These  products  become  heated  on  reaching  the  more  central 
portions  of  the  flame.  Then  the  carbon,  which  is  set  free  by 
the  decomposition  of  gases  rich  in  carbon,  is  brought  to  bright 
incandescence,  but  it  is  completely  burned  only  when  it  reaches 
the  exterior  envelope,  where  the  oxygen  is  in  excess.  A  simple 


STRUCTURE    OF   FLAME. 


221 


experiment  will  demonstrate  that  the  most  luminous  portion 
of  the  flame  holds  in  suspension  finely-divided  and  incandes- 
cent carbon.  If  a  porcelain  saucer  be  depressed  into  this 
portion,  the  carbon  will  be  deposited  on  the  vessel  in  the  form 
of  soot. 

It  is  this  solid  and  incandescent  carbon  which  causes  the 
luminosity  of  the  flame.  The  flame  of  hydrogen,  which  con- 
tains only  gaseous  products,  is  pale.  In  the  calcium  or  Drum- 
mond  light  it  produces  great  brilliancy  because  a  solid  body, 
lime,  is  heated  to  bright  incandescence.  When  the  carbon 
suspended  in  a  flame  is  in  excess  in  proportion  to  the  supply 
of  oxygen,  it  is  incompletely  burned,  and  is  carried  into  the 
air.  The  flame  then  smokes. 

At  the  base  of  the  cone,  carbon  monoxide  and  methane,  the 
first  products  of  the  decomposition  of  the  candle,  burn  on  con- 
tact with  the  air  at  dd'  with  a  bluish  flame. 

According  to  recent  experiments,  the  density  of  a  burning 
gas  is  not  without  influence  upon  the  lustre  of  the  flame.  The 
flame  of  hydrogen  is  luminous  when  that  gas  is  burned  under 
strong  pressure  (Frankland). 

Illuminating  gas  is  a  mixture  of  hydrogen  with  various  gas- 
eous hydrocarbons  and  a  small  proportion  of  carbon  monoxide. 
It  is  manufactured  by  the  destructive  dis- 
tillation of  bituminous  coal.  The  aqueous 
products  containing  ammonia,  and  the 
tarry  matters  formed  during  the  distilla- 
tion are  condensed,  and  the  gas  is  purified 
by  washing  with  water  and  passage  over 
slaked  lime  to  remove  sulphur  and  other 
impurities. 

Illuminating  gas  forms  an  explosive 
mixture  with  air,  but  if  the  mixture  be 
burned  as  it  is  formed,  the  resulting  flame 
will  be  almost  colorless  and  will  deposit 
no  soot,  the  whole  of  the  carbon  coming 
in  contact  with  sufficient  oxygen  for  its 
complete  combustion.  These  conditions 
are  fulfilled  in  the  Bunsen  burner  (Fig. 
89).  In  this  burner,  the  force  of  the 
escaping  gas-jet  draws  in  air  through  holes  immediately  oppo- 
site the  jet  in  a  wider  tube,  at  the  end  of  which  the  mixture  is 
burned. 

19* 


Fio.  89. 


222  ELEMENTS   OF   MODERN   CHEMISTRY. 

GENERAL  NOTIONS  UPON  THE  METALLOIDS. 

THEORY    OF    ATOMICITY. 

From  a  consideration  of  the  facts  acquired  in  the  study  of 
the  elements  known  as  metalloids,  we  may  deduce  certain  gen- 
eral consequences,  and  while  looking  back  on  the  field  over 
which  we  have  passed,  we  may  at  the  same  time  fix  certain 
landmarks  for  the  remainder  of  our  course. 

The  elements  which  we  have  studied  are  not  alike  in  their 
aptitude  to  enter  into  combination,  nor  in  the  general  characters 
of  their  compounds.  In  this  respect,  analogies  and  differ- 
ences have  been  established  between  them,  and  these  have 
become  the  basis  of  a  rational  classification.  Following  the 
example  of  Dumas,  we  have  arranged  these  elements  in  groups 
or  families,  uniting  in  the  same  group  those  which  are  related 
by  their  chemical  functions.  For  this  reason  boron  has  been 
separated  from  silicon  and  carbon,  since  it  differs  from  them 
so  far  as  concerns  the  composition  of  their  compounds.  The 
groups  thus  formed  are  as  follows : 

HYDROGEN.          OXYGEN.  NITROGEN.  BORON.  SILICON. 

SULPHUR.  PHOSPHORUS.  CARBON. 

FLUORINE.  SELENIUM.  ARSENIC. 

CHLORINE.  TELLURIUM.  ANTIMONY. 

BROMINE. 
IODINE. 

In  order  to  account  for  the  chemical  functions  of  all  these 
bodies,  that  is,  for  the  parts  which  they  play  in  their  combina- 
tions, we  must  first  consider  their  hydrogen  compounds.  They 
constitute  the  following  series  : 


HH 

H20 

H3N 

H4Si 

Hydrogen. 

Water. 

Ammonia.          Hydrogen  silicide. 

HC1 

H2S 

H3P 

H4C 

Hydrochloric 
acid. 

Hydrogen 
sulphide. 

Hydrogen 
phosphide. 

Hydrogen 
carbide. 

HBr 

H2Se 

H3As 

Hydrobromic 

Hydrogen 

Hydrogen  arsenide. 

acid. 

seleuide. 

HI 

H2Te 

H3Sb 

Hydriodic  acid. 

Hydrogen 

Hydrogen  antimonide. 

telluride. 

HF1 

Hydrofluoric  acid. 

THEORY   OF   ATOMICITY.  223 

It  is  seen  that  the  preceding  groups  are  characterized  by  the 
composition  of  their  hydrogen  compounds.  While  the  bodies 
of  the  first  group  combine  with  hydrogen  atom  for  atom,  those 
of  the  second  group  require  two  atoms  of  hydrogen,  those  of 
the  third  three,  and  those  of  the  fourth  four,  to  form  hydrogen 
compounds.  Hence  we  may  draw  the  conclusion  that  the  atoms 
of  these  metalloids  are  far  from  being  equivalent  in  their  power 
of  combination  with  hydrogen. 

The  atoms  of  chlorine,  bromine,  and  iodine  are  equivalent 
to  each  other  in  this  respect,  for  each  requires  but  one  atom 
of  hydrogen. 

The  atoms  of  oxygen,  sulphur,  etc.,  are  equivalent  to  each 
other,  for  each  combines  with  two  atoms  of  hydrogen. 

The  atoms  of  nitrogen,  phosphorus,  arsenic,  and  antimony 
are  equivalent  to  each  other,  for  each  of  them  unites  with  three 
atoms  of  hydrogen. 

Lastly,  the  atoms  of  carbon  and  silicon  are  equivalent,  for 
each  can  unite  with  four  atoms  of  hydrogen. 

But,  on  the  other  hand,  it  is  evident  that  the  atoms  of  chlo- 
rine, oxygen,  nitrogen  and  carbon  are  not  equivalent  to  each 
other,  as  regards  their  power  of  combination  with  hydrogen, 
since  each  of  them  unites  with  a  different  number  of  atoms  of 
that  body. 

In  this  respect  it  may  be  said  that 

1  atom  of  chlorine  is  equivalent  to  1  atom  of  hydrogen. 
1  atom  of  oxygen  "  2  atoms  " 

1  atom  of  nitrogen  "  3  atoms  " 

1  atom  of  carbon  "  4  atoms  " 

It  is  evident  that  the  capacity  of  combination  which  resides 
in  the  atoms  of  simple  bodies  and  by  which  they  attract  the 
atoms  of  hydrogen,  is  unequal.  Leaving  aside  its  intensity, 
this  force  is  exerted  in  different  degrees,  for  it  determines  the 
union  of  1  atom  of  chlorine,  oxygen,  nitrogen,  or  carbon,  with 
1,  2,  3,  or  4  atoms  of  hydrogen. 

This  number  of  hydrogen  atoms  is  the  measure  of  the  degree 
of  force  which  resides  in  the  atoms, — of  the  capacity  of  combi- 
nation which  they  possess  for  each  other. 

Hence  we  conclude  that 

The  atoms  of  chlorine  and  its  associates  are  monatomic  or  univalent. 
The  atoms  of  oxygen         "  "  diatomic  or  bivalent. 

The  atoms  of  nitrogen      "  "  triatomic  or  trivalent. 

The  atoms  of  carbon          "  "  tetratomic  or  quadrivalent. 


224  ELEMENTS   OF   MODERN   CHEMISTRY. 

The  capacity  of  combination  which  resides  in  the  atoms,  and 
which  is  exerted  in  such  different  manners  according  to  the 
nature  of  the  atoms,  is  called  atomicity.  Atomicity  is  the 
relative  equivalence  of  the  atoms ;  it  is  simple  or  multiple,  and 
if  we  consider  it  in  its  first  degree,  we  may  say  that  the  atoms 
of  chlorine  and  the  atoms  of  hydrogen  are  so  constituted  that 
a  single  atom  of  one  attracts  a  single  atom  of  the  other.  When 
they  combine,  they  exchange  in  some  manner  a  unit  of  satura- 
tion, and  in  the  combination  of  chlorine  and  hydrogen  two  of 
these  units  of  force  are  neutralized ;  two  units  of  saturation  or 
two  atomicities  are  exchanged:  the  atoms  of  chlorine  and  of 
hydrogen  are  univalent. 

The  force  which  resides  in  an  atom  of  oxygen  is  more  com- 
plex. It  attracts  two  atoms  of  hydrogen,  and  represents  the 
second  degree  of  capacity  of  combination,  and  we  may  say  that 
in  each  atom  of  oxygen  reside  two  atomicities,  which  are  satis- 
fied and  exchanged  when  this  atom  combines  with  two  atoms  of 
hydrogen.  Hence,  four  atomicities  are  satisfied  by  the  com- 
bination. 

Following  the  same  reasoning,  we  consider  that  a  triple  capa- 
city of  combination  is  active  in  an  atom  of  nitrogen  when  this 
atom  unites  with  three  atoms  of  hydrogen ;  and  that  six  atom- 
icities are  satisfied  by  the  combination. 

Lastly,  tetratomic  carbon  is  provided  with  four  atomicities, 
which  are  satisfied  by  the  four  atomicities  which  reside  in  four 
atoms  of  hydrogen. 

If  this  neutralization  or  exchange  of  two  units  of  saturation 
be  represented  by  a  hyphen,  we  will  have  the  following  formulae : 

H-C1  H-O-H  H  H 

Hydrochloric  acid.  Water.  I  I 

N  H-C-H 

/\  i 

H  H  H 

Ammonia.        Hydrogen  monocarbide. 

It  is  seen  that  in  the  formulae  for  water,  ammonia  and  hydro- 
gen monocarbide,  the  polyatomic  elements,  oxygen,  nitrogen 
and  carbon,  constitute,  as  it  were,  the  nuclei  around  which  the 
other  atoms  are  symmetrically  grouped. 

A  great  many  other  bodies  present  the  same  constitutions  as 
the  preceding ;  it  is  evident  that  a  given  element  in  any  com- 
pound may  be  replaced  by  another  element  having  the  same 
atomicity,  without  disturbing  the  equilibrium  of  the  atomicities. 


THEORY    OF   ATOMICITY.  225 

Indeed,  if  we  suppose  the  chlorine,  oxygen,  nitrogen,  and 
carbon  to  be  replaced  by  elements  of  corresponding  atomicities, 
we  will  have  the  series  of  hydrogen  compounds  already  con- 
sidered. All  of  the  bodies  which  are  classed  together  in  the 
series  belong  to  the  same  type.  Each  contains  an  equal  num- 
ber of  atomicities  for  the  same  number  of  atoms. 

According  to  the  principle  of  substitution  announced  above, 
it  is  evident  that  the  hydrogen  in  each  of  the  hydrogen  com- 
pounds under  consideration  may  be  replaced  by  another  mon- 
atomic  element,  and  the  compounds  thus  formed  will  still  belong 
to  the  primitive  types. 

So  considered,  a  great  number  of  compounds  possess  the 
same  constitution, — that  is,  the  same  molecular  structure, — 
as  hydrochloric  acid,  water,  ammonia,  and  methane  or  hydro- 
gen monocarbide.  Such  are  those  arranged  in  vertical  columns 
in  the  following  table : 

TTPEHCI  TYPEII20  TYPE  NH3  TYPE  H* 

C1-C1  H-O-H  K  Cl 

Free  chlorine.  Water.  I  I 

N  C1-C-C1 

/\  I 

H  H  Cl 

Potassium  amide.         Carbon  tetrachloride. 

K-C1  C1-0-C1  Cl  Cl 

Potassium  chloride.      Hypochlorous  oxide.  I  I 

P  Cl-Si-Cl 

/\  i 

Cl  Cl  Cl 

Phosphorus  trichloride.  Silicon  tetrachloride. 

K-I  H-O-K  Cl  H 

Potassium  iodide.  Potassium  hydrate.  I  I 

Sb  H-Si-H 

Ag-I  Ag-O-Ag        Cl^Cl  H 

Silver  iodide.  Silver  oxide.  Antimony  trichloride.     Hydrogen  sillcide. 

All  of  these  bodies  belong  to  the  respective  types  HC1,  H2O, 
NH3,  CH*,  the  first  three  of  which  were  established  by  Ger- 
hardt,  and  have  their  existence  explained  by  the  atomicity  of 
the  elements  ;  that  is,  by  the  varying  equivalence  of  their  atoms, 
measured,  in  the  present  examples,  by  the  number  of  hydrogen 
atoms  with  which  they  combine. 

One  atom  of  oxygen  is  equivalent  to  two  atoms  of  hydrogen 

K* 


226  ELEMENTS   OP   MODERN    CHEMISTRY. 

or  two  atoms  of  chlorine.  Hence,  in  the  preceding  combina- 
tions, two  atoms  of  chlorine  may  be  replaced  by  one  atom  of 
oxygen  without  changing  the  equilibrium  of  the  atomicities. 
Thus,  the  oxides  SiO2,C02,  correspond  to  the  chlorides  SiCl4, 
CC14,  and  belong  to  the  same  type.  The  four  atomicities  of 
an  atom  of  silicon  or  carbon  are  saturated  by  the  four  atomici- 
ties of  two  atoms  of  oxygen. 

The  trichlorides  of  phosphorus  and  antimony,  PCI3  and  SbCP, 
which  will  be  found  in  the  preceding  table,  require  an  impor- 
tant remark.  They  are  not  saturated  with  chlorine,  and  each 
may  combine  with  two  more  atoms  of  that  element,  producing 
the  compounds  PCI5  and  SbCl5. 

Thus,  while  phosphorus  exhausts  its  power  of  combination 
with  hydrogen  in  uniting  with  three  atoms  of  that  element  in 
PH3,  its  capacity  of  combination  with  chlorine  is  only  exhausted 
when  it  has  combined  with  five  atoms ;  while  it  plays  the  part 
of  a  triatoniic  element  in  hydrogen  phosphide,  it  is  pentatomic 
in  phosphorus  pentachloride. 

From  these  facts  it  follows  that  it  is  often  difficult  to  meas- 
ure in  an  absolute  manner  the  capacity  of  combination  which 
resides  in  an  atom;  for  that  capacity  varies  according  to  the 
nature  of  the  elements  upon  which  it  is  exerted.  Affinity  is 
an  elective  force.  A  given  element  does  not  attract  all  of  the 
other  elements  with  equal  facility ;  it  selects  certain  ones  by 
preference,  and  neglects  the  others.  With  one,  it  may  form 
but  a  single  compound ;  with  another,  it  may  form  several. 

Nitrogen  forms  with  hydrogen  but  one  combination,  ammo- 
nia, NHJ,  which  cannot  fix  any  more  atoms  of  hydrogen.  Sat- 
urated with  hydrogen  in  ammonia,  nitrogen  manifests  in  con- 
tact with  that  element  but  three  atomicities.  But  let  ammonia 
be  brought  in  contact  with  a  body  other  than  hydrogen,  hydro- 
chloric acid,  for  example,  and  it  will  combine  with  it,  forming 
ammonia  hydrochloride,  or  ammonium  chloride.  If  its  ca- 
pacity of  combination  is  exhausted  for  hydrogen,  HH,  it  is 
not  exhausted  for  hydrogen  combined  with  chlorine,  HC1. 
Thus,  an  atom  of  nitrogen  possesses  other  affinities  than  those 
which  it  manifests  for  hydrogen  in  ammonia.  While  nitrogen 
is  triatomic  in  ammonia  because  it  is  united  with  three  mon- 
atomic  atoms,  it  behaves  as  a  pentatomic  element  in  ammonium 
chloride. 

The  parts  which  polyatomic  elements  play  in  their  compounds 
may  be  expressed  by  accents  marking  the  number  of  atomici- 


THEORY   OF   ATOMICITY.  227 

ties  or  the  quantivalence  of  the  element,   as  shown  in   the 
following  formulae : 

0"H2    N'"H3    NVH4C1      P"CP         PVC15       CivO"2 

Water.    Ammonia.    Ammonium    Phosphorus       Phosphorus        Carbon 
chloride.       trichloride,     pentachloride.      dioxide. 

In  these  compounds,  as  has  been  remarked  before,  the  poly- 
atomic elements  form,  as  it  were,  the  nuclei  around  which  the 
other  elements  are  grouped.  This  is  an  important  idea,  since 
it  leads  to  the  determination  of  the  constitution  of  the  mole- 
cules, that  is,  the  arrangement  of  their  atoms.  The  considera- 
tions just  presented  concerning  the  functions  of  the  elements 
in  compounds  alone  permit  the  resolution  of  this  question ; 
they  alone  lead  to  the  discovery  of  the  relations  existing  be- 
tween the  atoms  in  their  combinations,  and  to  the  determina- 
tion of  their  relative  positions,  in  a  word,  to  the  revelation  of 
the  molecular  structure. 

The  following  developments  will  demonstrate  this  fact. 

We  will  reconsider  certain  of  the  combinations  above  men- 
tioned, which  have  been  taken  as  types. 

In  water,  an  atom  of  diatomic  oxygen  fixes  two  atoms  of 
hydrogen.  One  atom  of  oxygen  can  fix  two  atoms  of  any 
monatomic  element,  forming  compounds  belonging  to  the  same 
type  as  water ;  but  it  cannot  at  the  same  time  fix  a  monatomic 
element  and  a  diatomic  element.  In  other  words,  an  atom  of 
hydrogen  in  water  may  be  replaced  by  an  atom  of  chlorine, 
bromine,  iodine,  or  potassium,  but  not  by  an  atom  of  oxygen ; 
and  if  a  second  atom  of  the  latter  element  be  joined  to  the 
oxygen  of  water,  it  will  be  seen  that  there  remains  a  free  affin- 
ity which  may  be  satisfied  by  hydrogen.  Hydrogen  dioxide 
would  result. 

H-0"-H  H-0"-0"-H 

Water.  Hydrogen  dioxide. 

Hence,  we  draw  the  conclusion  that  in  hydrogen  peroxide, 
the  two  atoms  of  oxygen  are  combined  with  each  other,  and 
that  in  uniting  together  each  atom  loses  one  atomicity,  the  two 
others  being  satisfied  by  hydrogen. 

The  same  considerations  are  applicable  to  the  compounds  of 
chlorine  and  oxygen. 

Hypochlorous  acid  may  be  regarded  as  composed  of  an  atom 
of  chlorine  united  to  the  group  hydroxyl. 
d-0"-H  =  Cl(OH)' 

Hypochlorous  acid. 


228  ELEMENTS   OP   MODERN   CHEMISTRY. 

In  this  compound  the  chlorine  exchanges  one  unit  of  satu- 
ration with  the  oxygen  of  the  group  OH,  just  as  it  exchanges 
one  with  hydrogen  in  hydrochloric  acid:  it  is  monatomie  or 
univalent.  In  chloric  acid  it  is  combined  with  two  atoms  of 
oxygen  and  one  group,  OH.  It  exchanges  4  atomicities  with 
oxygen,  arid  one  with  the  group  OH : 

C1V0"2(OH)' 

Cbloric  acid. 

Chlorine  thus  manifests  5  atomicities  in  chloric  acid ;  but  it 
has  7  in  perchloric  acid. 

Clvii03(OH)' 

Perchloric  acid. 

Without  dwelling  on  these  considerations,  we  will  take  one 
more  example. 

In  hydrogen  phosphide,  one  atom  of  phosphorus  is  combined 
with  three  atoms  of  hydrogen ;  it  manifests  but  three  atomici- 
ties, and  these  could  not  neutralize  those  which  reside  in  three 
atoms  of  oxygen,  since  the  latter  possess  six  atomicities.  If, 
then,  three  atoms  of  diatomic  oxygen  were  united  with  one 
atom  of  triatomic  phosphorus,  it  is  clear  that  three  affinities 
would  remain  free,  one  in  each  of  the  three  atoms  of  oxygen. 
In  phosphorous  acid,  these  three  affinities  of  the  oxygen  atoms 
are  satisfied  by  three  atoms  of  hydrogen.  We  may  suppose 
that  in  the  molecule  of  this  compound,  the  phosphorus  is  the 
nucleus  around  which  are  grouped  three  atoms  of  oxygen,  each 
of  which  is  joined  also  to  one  atom  of  hydrogen. 

This  atomic  grouping  is  indicated  in  the  following  formulae : 

H  OH 

i  i 

P  P 

H/XH  HO  OH 

Hydrogen  phosphide.  Phosphorous  acid. 

This  hydrogen,  combined  with  the  oxygen  in  all  of  the  oxy- 
gen acids,  plays  invariably  the  same  part:  it  saturates  the  one 
atomicity  which  remains  free  in  one  atom  of  oxygen.  The 
oxygen  thus  combined  with  an  atom  of  hydrogen,  has  lost  one 
of  its  atomicities  by  the  fact  of  this  combination ;  it  still  retains 
one  in  the  group  OH,  which  represents,  as  it  were,  water  less 
one  atom  of  hydrogen.  • 

HOH  —  H  =  (OH)' 


THEORY   OF   ATOMICITY.  229 

This  group  is  named  hydroxyl,  and  it  is  evident  that, 
although  it  cannot  exist  by  itself,  it  may  play  the  part  of  a 
monatomic  element,  for  it  retains  one  free  atomicity.  It  may 
then  replace  a  monatomic  element,  such  as  hydrogen  or  chlo- 
rine. Indeed,  it  plays  an  important  part  in  the  constitution  of 
acids. 

If  we  consider  the  examples  which  have  already  been  dis- 
cussed, we  will  notice  that  it  is  this  hydroxyl  which,  by  com- 
bining with  an  element  or  group  of  elements  capable  of  forming 
acids,  confers  upon  them  the  characters  of  acids.  So  consid- 
ered, hypochlorous  acid  is  formed  by  the  union  of  hydroxyl 
with  an  atom  of  chlorine. 

Cl(OH)' 

Hypochlorous  acid. 

Sulphuric  acid  is  formed  by  the  union  of  two  hydroxyl  groups 
with  sulphurous  oxide,  and  represents  in  a  manner  sulphuryl 
chloride  in  which  the  two  atoms  of  chlorine  are  replaced  by 
two  hydroxyl  groups. 

C1  SO2  1  (OH)' 

Cl  b°  {  (OH/ 

Sulphuryl  chloride.  Sulphuric  acid. 

Phosphorous  acid  is  formed  by  the  union  of  three  hydroxyl 
groups  with  one  atom  of  phosphorus. 

Cl  (OH)' 


Cl  (OH)' 

Phosphorus  trichloride.  Phosphorous  acid. 

Lastly,  phosphoric  acid  results  from  the  union  of  three  hy- 
droxyl groups  with  one  atom  of  phosphorus  already  combined 
with  one  atom  of  oxygen  (phosphoryl). 

Cl  (  (OH)' 

Cl  O'TM  (OH)' 

Cl  ((OH)' 

Phosphoryl  trichloride.  •    Phosphoric  acid. 

Such,  according  to  the  theory  of  atomicity,  are  the  relations 
existing  between  the  atoms  of  certain  acids  ;  such,  in  other  words, 
is  the  constitution  of  these  acids.  It  would  be  easy  to  extend 
these  considerations  to  other  bodies,  but  the  examples  we  have 
chosen  are  sufficient  to  indicate  the  importance  of  the  idea  of 
atomicity,  when  it  is  applied  to  the  discovery  and  definition  of 

20 


( 


230  ELEMENTS    OF    MODERN    CHEMISTRY. 

the  part  played  by  each  element  in  a  given  compound.  By 
supposing  the  capacities  of  combination  of  chlorine,  oxygen, 
sulphur,  and  phosphorus  to  be  known,  we  have  been  able  to 
follow  these  bodies  in  their  most  important  combinations,  we 
have  seen  how  they  attract  and  group  around  themselves  other 
elements.  We  have  thus  been  able  to  penetrate  the  atomic 
structure  of  the  molecules,  and  have  built  up  as  it  were  the 
molecular  edifice.  It  must  be  remembered,  however,  that  the 
preceding  formulae  do  not  in  any  manner  represent  the  real 
positions  of  the  atoms  in  space.  Their  sole  object  is  to  indi- 
cate the  points  of  attachment  of  the  affinities,  and  consequently 
the  mutual  relations  between  the  atoms. 


METALS. 


THE  metals  are  elements  which  are  good  conductors  of  heat 
and  electricity,  and  are  endowed  with  a  peculiar  lustre,  which 
is  called  the  metallic  lustre.  This  definition,  it  will  be  ob- 
served, is  founded  upon  certain  physical  characters  rather  than 
upon  chemical  properties.  It  is  unsatisfactory  and  wanting  in 
exactness,  for  it  is  applicable  to  bodies  which  are  properly  con- 
sidered as  metalloids.  Such  is  antimony,  which  has  already 
been  described,  and  bismuth,  which  should  be  placed  beside 
antimony.  Indeed,  the  distinction  between  the  metals  and 
metalloids  is  not  so  well  marked  that  a  line  which  shall  sepa- 
rate these  two  classes  of  simple  bodies  may  be  sharply  drawn. 

Physical  Properties  of  the  Metals. — These  will  be  found 
in  the  table  on  page  232,  but  the  indications  there  given  may 
be  completed  by  certain  other  developments. 

The  metals  are  opaque,  but  their  opacity  is  not  absolute. 
A  sheet  of  gold-leaf  pressed  out  between  two  plates  of  glass 
allows  the  passage  of  a  green  light. 

Gold  possesses  a  brilliant  lustre  and  a  yellow  color,  but  it 
loses  this  lustre  when  it  is  reduced  to  a  minute  powder.  When, 
however,  this  powder  is  rubbed  with  a  hard  body,  when,  for 
example,  it  is  triturated  in  an  agate  mortar,  or  passed  under 
the  burnisher,  it  acquires  a  certain  degree  of  cohesion,  and 
again  assumes  its  lustre. 

It  is  thus  with  all  the  metals.  They  lose  their  metallic  lustre 
when  finely  divided  and  reassume  it  on  burnishing. 

The  yellow  color  of  gold  is  not  its  true  color ;  the  rays  which 
reach  the  eye  are  the  result  of  but  one  reflection,  but  if  light 
be  successively  reflected  from  ten  surfaces  of  gold,  the  metal 
will  appear  of  a  bright-red  color.  Under  the  same  circum- 
stances, copper  will  appear  scarlet,  zinc  indigo,  iron  violet,  and 
silver  pure  yellow  (B.  Prevost). 

Most  of  the  metals  may  be  crystallized.  Bismuth  is  the 
most  striking  example.  If  a  few  kilogrammes  of  pure  bismuth 
be  fused,  and  the  liquid  mass  be  allowed  to  cool  slowly,  the 

231 


232 


ELEMENTS    OF    MODERN    CHEMISTRY. 


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oft  at  ordinary 
temperatures. 


s  a 


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linn!*  i  I!  n 

OH^OCDOQPSOH  ^4       c-.  x>      S 


£  £ 


I  :-J  'bl| :  jr;l 


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GENERAL   PROPERTIES   OF   METALS. 


233 


metal  will  solidify  first  next  to  the  walls  of  the  vessel  and  on 
the  surface,  where  it  is  most  cooled.  If,  in  a  little  while,  the 
crust  which  covers  the  still  liquid  metal  be  pierced,  and  the 
latter  be  poured  out,  the  whole  of  the  interior  of  the  vessel 
will  be  found  covered  with  magnificent  crystals,  arranged  in 
hopper-like  pyramids,  and  presenting  brilliant,  rainbow-like 
colors. 

Other  metals,  such  as  copper,  lead,  antimony,  tin,  silver,  and 
gold,  may  be  crystallized  under  certain  conditions.  Some  of 
the  metals  are  found  crystallized  in  nature. 

Those  metals  which  may  be  beaten  or  rolled  into  thin  laminae 
are  said  to  be  malleable.  AA  (Fig.  90)  represent  two  steel 


rollers  capable  of  moving  on  their  axes  in  opposite  directions. 
A  plate  of  metal  engaged  between  them  will  be  drawn  in,  and 
the  rollod  sheet  will  pass  out  on  the  other  side  with  a  uniform 
thickness  equal  to  the  distance  between  the  two  rollers.  By 
diminishing  this  distance  more  and  more  by  means  of  the 
screws  BB,  the  sheet  may  gradually  be  reduced  in  thickness. 

Metals  which  may  be  drawn  out  into  wires  are  said  to  be 
ductile.  The  wire-drawing  machine  is  represented  in  Fig. 
91.  It  consists  of  a  steel  plate,  ff,  firmly  fixed  in  the  up- 
rights CC,  which  are  themselves  solidly  attached  to  a  bench. 
The  plate  is  pierced  with  a  series  of  holes  regularly  decreasing 
in  diameter.  The  wire  is  drawn  from  the  bobbin  A,  through 
the  holes  and  around  the  cylinder  B,  which  is  moved  by  power. 

That  a  metal  may  be  drawn  into  fine  wires,  it  is  necessary 
that  it  shall  offer  a  certain  resistance  to  rupture.  This  is  called 
the  tenacity  of  the  metal.  It  is  measured  by  suspending  weights 

20* 


234 


ELEMENTS    OP    MODERN    CHEMISTRY. 


at  the  extremities  of  wires  of  the  same  diameter.  Iron  is  the 
most  tenacious  of  metals. 

All  of  the  metals  are  fusible.  Some  of  them  are  volatile 
and  may  be  distilled  ;  among  the  latter  are  mercury,  potassium, 
sodium,  zinc,  and  cadmium.  All  of  the  metals  are  insoluble. 

Chemical  Properties  of  the  Metals. — The  metals  combine 
with  each  other  and  with  the  metalloids,  the  energy  with  which 
these  combinations  take  place  being  very  variable.  In  general, 


FIG.  91. 

the  metals  having  the  strongest  affinities  are  those  known  as  the 
alkaline  metals,  because  they  are  obtained  from  the  alkalies. 
Such  are  potassium  and  sodium. 

All  of  the  metals  combine  directly  with  chlorine.  The  chlo- 
rides thus  formed  do  not  all  possess  the  same  composition  ;  they 
contain  for  one  atom  of  metal  a  varying  number  of  chlorine 
atoms. 

A  similar  remark  applies  to  the  oxides  and  sulphides  formed 
by  the  union  of  oxygen  and  sulphur  with  the  metals.  The 
power  of  combination  of  the  latter  with  chlorine,  sulphur,  oxy- 
gen, etc.,  is  far  from  being  the  same.  In  other  words,  the  atoms 
of  the  metals  combine  unequally  with  the  atoms  of  chlorine, 
oxygen,  etc. ;  hence  it  follows  that  the  atomic  composition  of 
the  bodies  thus  formed  is  different.  If  the  metals  be  compared 
together  in  this  respect,  analogies  and  differences  will  be  estab- 
lished between  them,  which  become  the  basis  for  a  rational 
classification.  Those  metals  which  form  compounds  having 


EXTRACTION   OF   METALS.  235 

analogous  atomic  constitutions  are  put  into  the  same  group. 
Such  principles  as  these  have  guided  us  in  the  classification  of 
the  metalloids,  and  we  will  apply  them  to  the  metals  as  soon  as 
we  have  acquired  a  general  knowledge  of  their  compounds. 

Thenard  founded  a  classification  of  the  metals,  not  upon  their 
power  of  combination  considered  in  a  general  manner,  but  upon 
the  variable  energy  of  their  affinities  for  oxygen.  He  measured 
this  affinity: 

1.  By  the  facility  with  which  the  metals  attract  free  oxygen 
at  various  temperatures. 

2.  By  the  difficulty  with  which  the  oxides,  once  formed, 
abandon  their  oxygen. 

3.  By  the  greater  or  less  energy  with  which  the  metals  de- 
compose water. 

Following  these  principles,  Thenard  divided  the  metals  into  six 
classes.  It  cannot  be  denied  that  this  classification  presents  many 
practical  advantages,  but,  on  the  other  hand,  in  a  great  num- 
ber of  cases  it  does  not  recognize  the  best  established  analogies. 

Natural  State  and  Extraction  of  the  Metals, — Certain 
metals  are  found  in  nature  free  from  all  combination.  It  is 
thus  that  gold,  silver,  copper,  bismuth,  etc.,  are  met  with  in 
the  native  state. 

More  often  the  metals  are  found  combined  with  oxygen,  sul- 
phur, or  other  metalloids.  The  natural  sulphides  are  numerous 
and  abundant :  those  of  silver,  copper,  mercury,  lead,  and  zinc 
constitute  the  minerals  from  which  these  metals  are  ordinarily 
extracted. 

Iron  and  tin  are  obtained  from  their  oxides,  which  are  found 
in  nature. 

The  metals  are  often  found  in  saline  combinations,  in  the  form 
of  chlorides,  carbonates,  sulphates,  phosphates,  and  silicates. 

We  can  only  indicate  here  in  a  very  general  manner  the 
methods  by  the  aid  of  which  the  metals  are  extracted  from 
their  combinations. 

If  a  metal  is  to  be  obtained  from  its  oxide,  the  latter  is 
reduced  by  charcoal  at  a  high  temperature. 

If  the  ore  be  a  sulphide,  it  is  first  roasted,  that  is,  heated  in 
contact  with  the  air.  The  oxygen  of  the  air  then  acts  upon 
the  sulphur,  which  is  disengaged  in  the  form  of  sulphurous 
oxide,  and  upon  the  metal,  which  remains  in  the  form  of  oxide ; 
the  latter  is  afterwards  reduced  by  charcoal. 

The  metals  are  sometimes  obtained  from  their  chlorides  by 


236  ELEMENTS   OP   MODERN   CHEMISTRY. 

heating  the  latter  with  sodium,  which  combines  with  the  chlo- 
rine, forming  sodium  chloride. 

ALLOYS. 

The  combinations  of  the  metals  with  each  other  are  called 
alloys;  amalgams  are  the  alloys  formed  by  mercury.  These 
combinations  take  place  with  the  production  of  heat. 

If  a  small  quantity  of  mercury  be  heated  in  a  crucible  or  a 
capsule,  and  a  morsel  of  sodium  be  thrown  into  it,  the  latter 
dissolves  instantly  with  a  hissing  noise,  which  indicates  the 
disengagement  of  heat. 

By  employing  the  proper  proportions  of  mercury  and  so- 
dium, the  alloy  may  be  obtained  in  crystals  possessing  a  definite 
composition. 

Crystalline  combinations  of  zinc  and  antimony  are  known. 
The  most  interesting,  Sb'2Zn3,  contains  two  atoms  of  antimony 
for  three  atoms  of  zinc. 

It  is  necessary  to  state  that  more  generally  the  alloys  do  not 
present  the  characters  of  definite  compounds.  The  metals  seem 
to  alloy  each  other  in  all  proportions,  forming  mixtures  which 
are  more  or  less  homogeneous;  but  this  is  only  in  appearance, 
and  it  must  be  admitted  that  one  or  more  compounds  exist  in 
such  a  mixture,  remaining  dissolved  in  each  other,  or  mixed 
with  the  excess  of  one  of  the  metals.  Such  a  mixture  would 
form  a  sensibly  homogeneous  mass,  especially  when  the  molten 
mixture  had  been  suddenly  cooled.  But  if  the  cooling  be  slow, 
it  may  happen  that  the  less  fusible  definite  compounds  separate 
from  the  mixture  in  the  crystalline  form,  leaving  the  more 
fusible  compounds  which  still  remain  liquid.  Such  a  separa- 
tion often  takes  place  in  large  masses  of  melted  alloys  which 
are  allowed  to  cool  slowly.  The  process  is  called  liquation, 
and  it  may  be  readily  conceived  that  the  alloys  so  cooled  are 
far  from  homogeneous  in  composition  after  their  solidification. 

Reciprocally,  when  a  mass  composed  of  a  mixture  of  metals 
and  alloys  is  slowly  heated,  the  more  fusible  assume  the  liquid 
state  first,  and  separate  from  the  others. 

This  difference  between  the  fusing-points  of  the  various  defi- 
nite compounds  which  may  exist  in  an  alloy  is  taken  advantage 
of  in  the  arts  for  their  separation. 

Alloys  are  always  more  fusible  than  the  most  fusible  of  their 
component  metals. 


ALLOYS. 


237 


There  is  an  alloy  which  is  fusible  between  66  and  71° ;  it  is 
formed  of 

Cadmium 1  to  2  parts. 

Tin 2  parts. 

Lead 4  parts. 

Bismuth 7  to  8  parts. 

This  is  known  as  Wood's  alloy.    The  fusible  metal  of  Arcet 
is  composed  of 

Bismuth 8  parts. 

Lead 5  Parts- 

Tin 3  parts. 

It  melts  at  94.5°.     The  following  table  gives  the  composition 

of  the  principal  alloys : 

Gold 900 

Gold  com Copper 100 

Gold 750-920 

Gold  jewelry Copper 250-80 

Silver 900 

Silver  com [Copper 100 

(Silver 950 

Silver  plate j  Copper 50 

Silver 800 

Silver  jewelry Copper 200 

f  Copper    .......  93.5-95 

Bronze  medals -I  Tin     .     . 6-4 

(Zinc 0.5-1 

(Copper 100 

Gun-metal { Tin 10 

Copper 78 

Bell-metal { Tin 22 

.  .  (  Copper    . 67 

Speculum-metal j  Ti£r 33 

.   .        ,                                         (Copper    .'.'..*..      90-95 
Aluminium  bronze Aluminium 10-5 

Copper 90 

Red  brass 10 

;  ;  ;  :  ;  ;  ;    g 

{Copper    .......  50 

Zinc    ....'....  25 

Nickel 25 

(  Lead 80 

Type-metal j  Antimony 20 

!Tin 100 

Antimony 8 

Bismuth. 1 

Copper    4 

(  Tin 92 

Hard  pewter j  Lead 8 

Soft  pewter { £ead   '.'.'.'.'.'.     '.     '.      18 

(Tin 66 

Plumbers'  solder j  Lead 33 


238  ELEMENTS   OF   MODERN    CHEMISTRY. 


METALLIC   OXIDES   AND   HYDRATES. 

Formation  of  Metallic  Oxides, — The  metals  absorb  oxygen 
with  very  unequal  energy.  Many  of  them  become  oxidized 
when  exposed  to  the  air  at  temperatures  more  or  less  elevated. 
In  this  respect  it  is  important  to  distinguish  the  action  of  dry 
air  from  that  of  moist  air. 

Potassium  is  the  only  metal  that  absorbs  dry  oxygen  at  ordi- 
nary temperatures.  All  of  the  other  metals,  with  the  excep- 
tion of  silver,  gold,  and  platinum,  only  become  oxidized  in  the 
air  at  very  high  temperatures.  Melted  lead  absorbs  oxygen. 
Mercury  becomes  oxidized  at  about  350° ;  copper  at  a  dull-red 
heat. 

The  combination  often  takes  place  with  the  production  of 
luminous  heat.  Iron  burns  in  oxygen,  but  it  is  necessary  that 
the  metal  be  first  heated  to  bright  redness  that  the  combustion 
may  take  place. 

However,  the  finely-divided  iron  that  is  obtained  by  reducing 
oxide  of  iron  in  a  current  of  hydrogen  at  a  comparatively  low 
temperature,  will  take  fire  when  exposed  to  the  air  at  ordi- 
nary temperatures.  It  is  pyrophoric,  and  the  fine  state  of 
division  of  the  metal  favors  the  oxidation.  If  the  powder  be 
projected  into  the  air,  each  particle  takes  fire  and  burns  with  a 
bright  flash. 

A  bright  sheet  of  iron  will  indefinitely  preserve  its  brilliant 
surface  in  dry  air,  but  if  a  drop  of  water  be  placed  upon  it,  or 
if  it  be  exposed  to  the  action  of  a  moist  atmosphere,  rust  makes 
its  appearance  in  a  short  time.  This  rust  is  ferric  hydrate, 
for  the  metal  has  at  the  same  time  absorbed  oxygen  and 
water. 

It  is  generally  admitted  that  it  is  the  oxygen  of  the  air  dis- 
solved in  the  water  that  first  fixes  upon  the  metal,  and  that 
the  combination  is  favored  by  the  presence  of  carbon  dioxide. 
However  it  may  be,  the  spot  of  rust  once  formed  constitutes  a 
Voltaic  couple  with  the  iron  itself,  and  the  current  so  estab- 
lished decomposes  the  water.  The  oxidation  then  proceeds 
rapidly,  the  oxygen  of  the  decomposed  water  combining  with 
the  metal. 

It  is  possible  that  hydrogen  dioxide  may  play  a  part  in  oxi- 
dations ;  it  may  be  formed  as  a  secondary  product  during  the 


METALLIC   OXIDES   AND    HYDRATES.  239 

decomposition  of  the  water,  and  fix  directly  upon  the  metals, 
converting  them  into  hydrates  (Weltzien). 

Fe2     +     3H202     =     Fe206H6 

Iron.        Hydrogen  dioxide.        Ferric  hydrate. 

Mg    +     H202     =    Mg02H2 

Magnesium.  Magnesium  hydrate. 

Indeed,  the  oxidation  of  metals  in  moist  air  always  produces 
hydrates  and  not  oxides. 

Composition  and  Classification  of  the  Oxides. — It  has 
already  been  remarked  that  the  metals  differ  as  to  the  number 
of  oxygen  atoms  with  which  they  combine ;  besides  this,  the 
same  metal  may  form  several  compounds  with  oxygen ;  differ- 
ent degrees  of  oxidation.  Hence  the  oxides  present  different 
compositions,  and  the  differences  are  important,  since  they  exer- 
cise a  marked  influence  upon  the  properties  of  the  compounds. 

1.  Certain  oxides  present  the  same  atomic  constitution  as 
water.     Two  atoms  of  metal  are  combined  with  one  atom  of 
oxygen. 

K20  potassium  oxide. 
Na20  sodium  oxide. 
Li20  lithium  oxide. 
T120  thallium  oxide. 
Ag20  silver  oxide. 

2.  One  atom  of  certain  metals  can  combine  with  one  atom 
of  oxygen ;  the  oxides  of  the  general  formula  MO  result. 

BaO  barium  oxide. 
SrO  strontium  oxide. 
CaO  calcium  oxide. 
MgO  magnesium  oxide. 
MnO  manganous  oxide. 
FeO  ferrous  oxide. 
ZnO  zinc  oxide. 
PbO  lead  oxide. 
CuO  cupric  oxide. 
HgO  mercuric  oxide. 
SnO  stannous  oxide. 

The  metallic  oxides  containing  but  one  atom  of  oxygen  are 
generally  energetic  bases ;  that  is,  they  react  energetically  with 
the  acids,  forming  salts.  They  are  sometimes  called  basic  oxides. 

3.  The  sesquioxides  are  those  which  contain  two  atoms  of 
metal  and  three  atoms  of  oxygen.     Such  is  antimony  oxide, 
that  has  already  been  studied ;  the  oxides  of  bismuth,  gold,  etc., 
present  an  analogous  composition. 


240  ELEMENTS   OF   MODERN   CHEMISTRY. 

Sb203  antimony  sesquioxide. 
Bi203  bismuth  sesquioxide. 
Au203  gold  sesquioxide. 

Fe203  ferric  oxide. 
Mn203  manganic  oxide. 
Cr203  chromic  oxide. 
A1203  aluminium  oxide. 

4.  A  large  number  of  oxides  contain  two  atoms  of  oxygen. 

BaO2  barium  dioxide. 
SrO2  strontium  dioxide. 
MnO2  manganese  dioxide. 
PbO2  lead  dioxide. 

SnO2  stannic  oxide. 

The  first  four  dioxides  are  incapable  of  uniting  with  acids  to 
form  corresponding  salts.  Dumas  called  them  singular  oxides. 
When  manganese  dioxide  is  heated  with  sulphuric  acid,  oxygen 
is  disengaged,  and  manganous  sulphate  is  formed,  which  corre- 
sponds not  to  the  dioxide,  but  to  manganous  oxide. 

H'SO*     +       MnO2       ==       MnSO      +     H20     +     0 

Sulphuric  acid.    Manganese  dioxide.    Manganous  sulphate. 

Under  the  same  circumstances,  the  other  singular  oxides  act 
in  the  same  manner. 

As  to  stannic  oxide,  it  is  the  anhydride  of  a  metallic  acid. 

SnO2  +  H20  =  H2Sn03 

Stannic  acid. 

5.  The  oxides  which  contain  three  atoms  of  oxygen  possess 
acid  characters  still  more  marked  than  stannic  oxide.     Man- 
ganese trioxide,  MnO3,  is  known.     Ferric  and  chromic  anhy- 
drides present  the  same  composition. 

MnO3  manganese  trioxide,  or  manganic  anhydride. 
CrO3  chromium  trioxide,  or  chromic  anhydride. 
FeO3  iron  trioxide,  or  ferric  anhydride. 

6.  There  is  a  class  of  oxides  still  more  complex  than  the 
preceding;  they  can  be  regarded  as  formed  by  the  union  of 
two  oxides,  and  they  have  been  named  saline  oxides.    Such  are 

Manganoso-manganic   oxide  Mn30*  =  Mn203  +  MnO,  or   red  oxide   of 

manganese. 
Diplumboso-pluuibic  oxide  Pb304  =  PbO2  +  2PbO,  or  red  oxide  of  lead. 

The  first  contains  one  molecule  of  a  sesquioxide,  combined 
with  one  molecule  of  a  monoxide ;  the  second,  one  molecule  of  a 
dioxide  and  two  molecules  of  a  monoxide. 


METALLIC   OXIDES. 


241 


Chemical  Properties  of  the  Oxides. — Some  of  the  oxides 
are  fixed,  that  is,  undecomposable  by  heat;  others  lose  the 
whole  or  a  part  of  their  oxygen  at  temperatures  more  or  less 
elevated.  The  oxides  of  the  noble  metals,  such  as  silver,  gold, 
and  platinum,  are  decomposed  by  heat  alone  into  metal  and 
oxygen.  We  have  seen  that  mercuric  oxide  is  decomposed  by 
a  dull-red  heat.  Many  of  the  oxides  that  contain  two  or  three 
atoms  of  oxygen  lose  a  part  of  the  latter  element  when  heated 
to  redness.  Such  are  the  dioxides  of  manganese,  lead,  and 
barium. 

The  oxides  containing  but  one  atom  of  oxygen  are  among 
the  most  stable.  Some  of  them  absorb  oxygen  when  they  are 
heated  in  contact  with  air,  forming  higher  oxides.  Among 
these  are  manganous,  ferrous,  plumbous,  and  stannous  oxides. 

Hydrogen  reduces  the  greater  number  of  the  oxides  at  tem- 
peratures more  or  less  elevated ;  water  is  formed,  and  the  metal 
is  set  at  liberty. 

If  a  current  of  dry  hydrogen  be  passed  over  ferric  oxide 
heated  in  a  glass  bulb  (Fig.  92),  the  oxide  is  reduced,  and  a 


FIG.  92. 

black  powder  is  obtained  which  is  finely  divided  and  pyropho- 
ric  iron.  Vapor  of  water  escapes  at  the  same  time  by  the 
drawn-out  point  of  the  bulb. 


Fe203 

Ferric  oxide. 


3H2  =  3H20 


21 


2Fe 

Iron. 


242  ELEMENTS   OF   MODERN   CHEMISTRY. 

The  ferric  oxide  may  be  replaced  by  cupric  oxide,  CuO.  If 
this  oxide  be  heated  in  a  current  of  hydrogen,  it  is  reduced, 
and  the  action  is  so  energetic  that  it  gives  rise  to  the  produc- 
tion of  luminous  heat. 

Carbon  reduces  the  greater  number  of  the  oxides  with  for- 
mation of  either  carbon  dioxide  or  monoxide.  It  is  even  more 
energetic  in  its  action  than  hydrogen,  for  it  decomposes  oxides 
which  are  irreducible  by  the  latter  element,  such  as  those  of 
potassium  and  sodium.  The  oxides  of  calcium,  barium,  stron- 
tium, magnesium,  and  aluminium  are  irreducible  by  carbon. 
The  other  oxides  require  for  reduction  a  temperature  more  or 
less  elevated,  according  to  the  force  with  which  they  retain 
their  oxygen.  If  the  reduction  be  difficult,  a  high  temperature 
is  required^  and  carbon  monoxide  is  formed;  otherwise  carbon 
dioxide  is  the  product. 

A  small  quantity  of  cupric  oxide  may  be  reduced  by  char- 


FIG.  93. 

coal  by  heating  the  mixture  in  a  glass  tube  by  the  aid  of  a 
spirit-lamp  (Fig.  93).     Carbon  dioxide  is  disengaged. 

2CuO     +  C  ==  2Cu  -f  CO2 

Cupric  oxide.  Copper. 

But  to  reduce  zinc  oxide  by  charcoal,  the  mixture  must  be 


METALLIC    OXIDES. 


243 


heated  to  bright  redness  in  a  clay  or  iron  retort,  and  in  this 
case  carbon  monoxide  is  evolved. 

ZnO     -f  C  —  Zn  +  CO 

Zinc  oxide.  Zinc. 

Chlorine  decomposes  nearly  all  of  the  oxides  at  a  high  tem- 
perature. It  drives  out  the  oxygen  and  combines  with  the 
metal,  forming  a  chloride.  Some  of  the  oxides  are  irreducible 
by  carbon,  and  resist  also  the  action  of  chlorine.  Such  an 
oxide  is  aluminium  oxide,  or  alumina.  But  if  these  oxides 
be  submitted  to  the  simultaneous  action  of  chlorine  and  carbon 
at  a  high  temperature,  they  are  converted  into  chlorides,  and 
carbon  monoxide  is  disengaged. 

An  intimate  mixture  of  alumina  and  charcoal  may  be  intro- 
duced into  a  porcelain  tube,  BB  (Fig.  94),  which  is  heated  to 


FIG.  94. 

bright  redness,  and  a  current  of  dry  chlorine  then  passed 
through.  In  this  case,  carbon  monoxide  is  disengaged,  while 
aluminium  chloride  is  formed  and  volatilizes  and  may  be  con- 
densed in  a  cooled  receiver. 

Sulphur  decomposes  all  of  the  oxides  except  alumina  and  its 
analogues.  The  reaction  takes  place  at  a  high  temperature, 
and  gives  rise  to  the  formation  of  a  sulphide  and  sulphurous 
oxide,  or  a  sulphide  and  a  sulphate  if  the  latter  be  not  decom- 
posable by  heat. 


244  ELEMENTS   OF   MODERN   CHEMISTRY. 

If  sulphur  be  heated  with  cupric  oxide,  cupric  sulphide  is 
formed  and  sulphurous  oxide  is  evolved. 

2CuO     -f     3S     =     2CuS     -f     SO2 

Cupric  oxide.  Cupric  sulphide. 

However,  if  calcium  oxide  (lime)  or  lead  oxide,  PbO,  be 
heated  with  sulphur,  a  sulphate  and  a  sulphide  are  formed. 

4CaO     +     2S2     =     3CaS    '+     CaSO 

Calcium  oxide.  Calcium  sulphide.    Calcium  sulphate. 

Action  of  Water  upon  the  Oxides — Metallic  Hydrates 
and  Acids. — If  some  fragments  of  barium  oxide  (baryta)  be 
sprinkled  with  cold  water,  an  energetic  reaction  immediately 
takes  place.  The  water  unites  with  the  metallic  oxide  with  so 
much  energy  that  the  heat  disengaged  is  sufficient  to  convert 
a  portion  of  the  water  into  vapor.  The  barium  oxide  is  con- 
verted into  hydrate. 

BaO     +     H20     =     Ba(OH)2 

Barium  oxide.  Barium  hydrate. 

In  the  same  manner,  the  oxides  of  potassium  and  sodium 
energetically  absorb  the  elements  of  water,  being  converted 
into  hydrates. 

K20     +     H20     =     2KOH 

Potassium  oxide.  Potassium  hydrate. 

The  hydrates  of  potassium  and  sodium  are  soluble  in  water 
and  their  solutions  are  caustic,  changing  tincture  of  violet  to 
a  green  color  and  restoring  the  blue  color  to  reddened  litmus 
solution.  These  hydrates  constitute  the  alkalies. 

The  hydrates  of  barium,  strontium,  and  calcium  are  likewise 
soluble  in  water  to  a  certain  extent,  and  their  solutions  are  also 
somewhat  caustic. 

Other  hydrates  are  insoluble ;  they  may  be  obtained  by  double 
decomposition  by  precipitating  the  corresponding  salts  with  an 
alkali. 

If  a  solution  of  potassium  hydrate  be  poured  into  a  solution 
of  cupric  sulphate,  a  light-blue  precipitate  of  cupric  hydrate  is 
formed. 

CuSO*.    -f-      2KOH      =      K2S04      -f      Cu(OH)2 

Cupric  sulphate.          Potassium  hydrate.    Potassium  sulphate.         Cupric  hydrate. 

But  if  this  precipitate  be  heated,  even  .in  the  liquid  in 
which  it  was  formed,  it  changes  brown,  and  is  converted  into 
oxide  by  losing  its  water. 

Cu(OH)2  —  H2O  =  CuO 


SULPHIDES.  245 

A  great  number  of  metallic  hydrates  undergo  the  same 
decomposition  when  they  are  heated. 

There  are  true  metallic  acids  which  contain  the  elements  of 
an  oxide  plus  the  elements  of  water.  Such  are 

H2O04     =     CrO3     -f     H2O 

Chromic  acid.     Chromium  trioxide. 

H2MnO*     =     MnO8     +     H20 

Manganic  acid.    Manganese  trioxide. 

As  far  as  their  constitution  is  concerned,  these  metallic  acids 
may  be  compared  to  sulphuric  acid. 

H2SO*  =  SO3  +  H20 

They  also  resemble  sulphuric  acid  in  their  chemical  func- 
tions ;  each  contains  two  atoms  of  basic  hydrogen,  that  is,  two 
atoms  of  hydrogen  which  are  replaceable  by  a  metal. 


SULPHIDES. 

Sulphur  has  a  great  tendency  to  unite  with  the  metals,  and 
the  union  often  takes  place  with  a  vivid  evolution  of  heat. 
Copper-turnings  and  iron-filings  burn  in  the  vapor  of  sulphur. 
The  phenomena  which  favor  or  determine,  and  those  which 
accompany  this  combination,  have  already  been  indicated,  and 
we  have  seen  that  the  presence  of  a  small  quantity  of  water 
favors  chemical  union  in  a  mixture  of  sulphur  and  iron-filings. 

Certain  metals,  such  as  aluminium,  zinc,  and  gold,  resist  the 
action  of  sulphur  even  at  high  temperatures. 

In  composition  the  sulphides  are  analogous  to  the  oxides.     • 

The  more  important  of  the  transformations  which  they  may 
undergo  are  the  following: 

Oxygen  decomposes  all  of  the  sulphides  at  a  temperature 
more  or  less  elevated. 

Finely-divided  potassium  sulphide,  obtained  by  calcining  the 
sulphate  with  an  excess  of  charcoal,  is  a  black  powder,  but  it 
becomes  incandescent  on  contact  with  oxygen,  and  if  thrown 
into  the  air  it  produces  a  shower  of  sparks.  It  is  known  as 
Gay-Lussac's  pyrophorus.  Its  fine  state  of  division  favors  the 
absorption  of  oxygen,  and  the  latter  converts  it  into  sulphate. 
K2S  -f  0*  =  K2S04 

Potassium  sulphide.  Potassium  sulphate. 

Dry  oxygen  acts  in  the  same  manner  upon  all  the  sulphides 
21* 


246  ELEMENTS    OF    MODERN    CHEMISTRY. 

when  the*  corresponding  sulphates  are  stable  at  high  tempera- 
tures. In  the  contrary  case,  sulphurous  oxide  is  formed,  and 
a  residue  of  oxide  or  even  of  metal  is  obtained,  if  the  oxide  be 
decomposable  by  heat. 

If  zinc  sulphide  be  roasted,  it  is  converted  into  zinc  oxide, 
and  sulphurous  oxide  is  evolved ;  but  if  sulphide  of  mercury 
be  heated  in  a  current  of  air,  metallic  mercury  is  obtained. 

HgS     +     O2     =     Hg     +     SO2 

Mercuric  sulphide.  Mercury. 

Moist  oxygen  acts  upon  the  sulphides  more  readily  than  the 
dry  gas.  It  unites  with  them  at  ordinary  temperatures,  form- 
ing sulphates. 

FeS     +    0*    =     FeSO4 

Sulphide  of  iron.  Ferrous  sulphate. 

Chlorine  attacks  all  of  the  sulphides,  forming  metallic  chlo- 
rides and  sulphur  chloride,  if  the  dry  method  be  employed,  or 
with  deposition  of  sulphur  if  the  reaction  take  place  in  presence 
of  water. 

Water  dissolves  the  alkaline  sulphides  as  well  as  those  of  cal- 
cium, barium,  and  strontium ;  the  sulphides  of  the  other  metals 
are  insoluble  in  water. 

Hydrogen  sulphide  combines  with  certain  sulphides,  convert- 
ing them  into  sulphydrates.     The  analogy  will  be  noticed  be- 
tween this  reaction  and  that  of  water  upon  the  oxides. 
K2S     +     IPS     =     2KSH 

Potassium  sulphide.  Potassium  sulphydrate. 

K2O     +     IPO     =     2KOH 

Potassium  oxide.  Potassium  hydrate. 

CHLORIDES. 

Chlorine,  bromine,  and  iodine  form  with  the  metals  com- 
pounds which  possess  the  appearance  and  certain  properties  of 
salts.  Indeed,  common  salt,  or  sodium  chloride,  has  given  the 
name  to  the  entire  class  of  saline  compounds.  Hence  Berze- 
lius  named  chlorine,  bromine,  and  iodine  the  halogen  bodies, 
and  called  their  combinations  with  the  metals  the  haloid  salts. 
Thus  he  admitted  the  relation  between  these  compounds  and 
the  true  salts,  while  at  the  same  time  distinguishing  them  by  a 
particular  name,  for  while  they  resemble  the  salts  in  their  prop- 
erties, they  differ  from  them  in  composition.  This  subject  will 
be  more  fully  considered  farther  on. 


CHLORIDES. 


247 


Composition,  —  All  of  the  metals,  with  the  exception  of  plat- 
inum, combine  directly  with  free  chlorine,  but  all  do  not  com- 
bine with  it  in  the  same  atomic  proportions,  and  often  the  same 
metal  forms  several  distinct  combinations  with  this  element. 
Hence  the  differences  in  the  composition  of  the  chlorides. 
They  are  formed  by  the  union  of  an  atom  of  metal  with  one, 
two,  three,  four,  five,  or  six  atoms  of  chlorine. 

KC1        CaCP         SbCl3         SnCl4  SbCl5  Mod6 

Potassium       Calcium         Antimony  Tin 

chloride.        chloride.       trichloride,    tetrachloride. 

NaCl      Fed2         Bid3         TiCl4 

Sodium       Ferrous          Bismuth         Titanium 
chloride,     chloride.       trichloride,     tetrachloride. 


CaCP 

Calcium 
chloride. 

Fed2 

Ferrous 
chloride. 

AgCl     ZnCP 

Silver  Zinc 

chloride.       chloride, 


SbCl3 

Antimony 
trichloride, 

Bid3 

Bismuth 
trichloride, 

AuCP        PtCl* 

Gold  Platinum 

trichloride,    tetrachloride. 


SbCl5 

Antimony        Molybdenum 
pentachloride.    hexachloride. 


To  these  chlorides  must  be  added  those  which  are  formed 
by  the  union  of  two  atoms  of  metal  with  two  or  six  atoms  of 
chlorine. 

(VCP 

Cuprous  chloride. 


Hg2CP 

Mercurous  chloride. 


APC16 

Aluminium  chloride. 

Cr2Cl6 

Chromic  chloride. 

Fe2Cl6 

Ferric  chloride. 


Cuprous  chloride  and  mercurous  chloride  contain  for  the 
same  quantity  of  chlorine  twice  as  much  metal  as  cupric  chlo- 
ride, CuCP,  and  mercuric  chloride,  HgCP. 

In  the  first,  two  atoms  of  copper  or  mercury  are  combined 
together  to  fix  two  atoms  of  chlorine,  and  these  two  atoms  of 
metal  remain  thus  associated  in  all  the  cuprous  and  mercurous 
compounds.  It  is  the  same  in  the  chloride  of  aluminium,  and 
in  chromic  and  ferric  chlorides.  Each  of  them  contains  two 
atoms  of  metal  intimately  associated,  and  combined  as  a  whole 
with  six  atoms  of  chlorine. 

The  same  metal  may  form  several  combinations  with  chlorine. 

Thallium  combines  with  one  or  three  atoms  of  chlorine. 

Tin  and  platinum  combine  with  two  or  four  atoms  of  chlorine. 

Antimony  combines  with  three  or  five  atoms  of  chlorine. 

Physical  Properties  of  the  Chlorides.  —  Most  of  the  chlo- 
rides are  solid  and  possess  the  aspect,  color,  and  physical  prop- 
erties of  the  salts  of  the  same  metal.  Nearly  all  are  crystalline 
and  soluble  in  water.  Only  the  chloride  of  silver,  mercurous 


248  ELEMENTS   OF   MODERN    CHEMISTRY. 

and  cuprous  chlorides  are  insoluble ;  plumbic  chloride  and  thal- 
lous  chloride  are  but  slightly  soluble  in  water. 

Certain  metallic  chlorides  are  liquid  at  ordinary  tempera- 
tures. Such  are  the  tetrachlorides  of  tin  and  titanium.  Some, 
like  the  chlorides  of  zinc  and  bismuth,  are  solid,  but  fusible  at 
low  temperatures.  These  latter  were  formerly  designated  as 
metallic  butters. 

Most  of  the  chlorides  are  fusible  at  high  temperatures,  and 
many  of  them  are  volatile  and  can  be  distilled  without  altera- 
tion. It  is  thus  with  the  liquid  chlorides,  with  the  chlorides 
of  zinc,  bismuth,  mercury,  etc. 

Chemical  Properties. — As  a  rule,  the  chlorides  are  very 
stable.  Only  the  chlorides  of  certain  of  the  precious  metals, 
as  those  of  gold  and  platinum,  are  entirely  decomposed  by  a 
high  temperature.  Some  of  the  higher  chlorides  lose  chlorine 
when  calcined,  and  are  converted  into  lower  chlorides.  Thus, 
cupric  chloride  is  converted  into  cuprous  chloride  when  heated 
out  of  contact  with.  air. 

A  great  number  of  the  chlorides  are  reduced  when  they  are 
heated  in  a  current  of  hydrogen.  In  this  case,  hydrochloric 
acid  is  disengaged,  and  the  metal  remains.  Thus,  hydrogen 
removes  the  chlorine  from  the  chlorides  of  silver  and  iron. 
These  decompositions  are  determined  by  the  powerful  affinity 
of  chlorine  for  hydrogen. 

The  action  of  the  metals  upon  the  chlorides  gives  rise  to 
interesting  phenomena  which  are  worthy  of  study. 

If  corrosive  sublimate,  which  is  mercuric  chloride,  be  mixed 
with  powdered  tin  and  the  mixture  be  heated  in  a  small  glass 
retort  provided  with  a  receiver,  a  liquid  will  soon  collect  in  the 
latter  which  diffuses  thick  vapors  in  the  air.  It  is  the  tetra- 
chloride  of  tin,  called  by  the  ancient  chemists  "  fuming  liquor 
of  Libavius."  It  is  formed  by  the  decomposition  of  the  mer- 
curic chloride,  which  gives  its  chlorine  to  the  tin,  metallic 
mercury  being  at  the  same  time  set  free. 

Bismuth  decomposes  mercuric  chloride  in  the  same  manner 
when  the  two  substances  are  heated  together.  These  experi- 
ments are  conducted  in  the  dry  way.  They  may  be  modified 
by  operating  in  the  presence  of  water,  in  which  we  have  re- 
marked that  most  of  the  chlorides  are  soluble;  it  is* thus  with 
mercuric  chloride. 

If  a  plate  of  copper  be  plunged  into  a  solution  of  this  body, 
it  at  once  becomes  covered  with  a  layer  of  metallic  mercury. 


CHLORIDES.  •  249 

That  metal  is  displaced  from  its  combination  by  the  copper, 
which  combines  with  the  chlorine :  cupric  chloride  is  formed, 
and  after  the  lapse  of  some  time,  the  liquid  will  contain  only 
that  compound.  It  becomes  green,  and  if  a  plate  of  zinc  be 
plunged  into  it,  the  copper  will  be  precipitated  in  its  turn,  and 
the  zinc  will  combine  with  the  chlorine  and  enter  the  solution ; 
the  liquid  then  contains  zinc  chloride. 

Thus,  the  metals  reciprocally  displace  each  other  from  their 
solutions,  according  to  the  energy  of  their  affinities.  In  this 
case  it  is  the  possession  of  the  chlorine  for  which  they  antago- 
nize each  other,  the  stronger  driving  out  the  weaker.  It  must 
be  remarked  that  in  this  respect  the  chlorides  behave  in  the 
same  manner  as  the  oxygen  salts. 

This  analogy  is  continued  in  innumerable  reactions.  Solu- 
tions of  the  chlorides  enter  into  double  decompositions  like 
solutions  of  the  true  salts.  If  potassium  hydrate  be  added  to 
a  solution  of  either  cupric  sulphate  or  cupric  chloride,  in  each 
case  a  light-blue  precipitate  of  cupric  hydrate  is  obtained. 

CuSO4     4-     2KOH     =    K2SO     -f     Cu(OH)2 

Cupric  sulphate.     Potassium  hydrate.  Potassium  sulphate.     Cupric  hydrate. 

CuCP     -f     2KOH     =     2KC1     -f     Cu(OH)2 

Cupric  chloride.  Potassium  chloride. 

But  cupric  chloride  resembles  the  sulphate  in  still  another 
property.  When  perfectly  pure  it  is  yellowish.  If  it  be  moist- 
ened with  water,  it  becomes  heated  and  assumes  a  green  color. 
It  has  combined  with  water,  and  will  dissolve  if  enough  of  that 
liquid  be  added.  A  green  liquor  is  thus  obtained,  which  de- 
posits, by  spontaneous  evaporation,  magnificent  green  prisms. 
These  crystals  are  hydrated  cupric  chloride.  They  contain 
water  of  crystallization,  and  can  only  exist  on  that  condition. 
It  is  the  same  with  the  crystals  of  cupric  sulphate. 

Thus,  certain  chlorides  are  capable  of  taking  water  of  crys- 
tallization like  the  true  salts. 

We  may  complete  the  analogy  by  one  more  characteristic. 

1.  If  a  solution  of  aluminium  sulphate  be  added  to  a  con- 
centrated solution  of  potassium  sulphate,  and  the  mixture  be 
agitated,  an  abundant  crystalline  deposit  is  obtained.     This  is 
a  double  salt, — potassium  and  aluminium  sulphate,  or  alum. 

2.  If  a  solution  of  platinic  chloride  be  added  to  a  concen- 
trated solution  of  potassium  chloride,  a  yellow  precipitate  is 

L* 


250  ELEMENTS    OF   MODERN    CHEMISTRY. 

formed  at  once.  It  is  the  double  chloride  of  potassium  and 
platinum,  which  contains  all  of  the  elements  of  two  molecules 
of  potassium  chloride  and  one  molecule  of  platinic  chloride. 
This  example  shows  that  the  chlorides  can  combine  together, 
forming  double  chlorides,  just  as  the  true  salts  may  combine 
together  to  form  double  salts. 


SALTS. 

Definition. — The  salts  are  formed  by  the  substitution  of 
metal  for  the  hydrogen  of  the  acids,  and  they  result  from  the 
action  of  the  acids  upon  the  metallic  oxides  or  hydrates.  The 
name  acid  applies  to  two  classes  of  compounds:  the  first  are 
formed  by  the  union  of  hydrogen  with  a  strongly  electro-nega- 
tive element,  such  as  chlorine  or  bromine ;  these  are  the  hy- 
dr acids.  Such  are  hydrochloric  acid,  HC1,  and  hydrobromic 
acid,  HBr. 

The  acids  of  the  other  class  are  more  complicated,  contain- 
ing hydrogen  united  with  a  strongly  electro-negative  oxidized 
group,  that  is,  a  group  of  atoms  formed  by  oxygen  and  another 
element;  these  are  the  oxacids.  Such  are  nitric  acid,  HNO3, 
and  sulphuric  acid,  H2S04. 

These  two  classes  of  acids  behave  in  the  same  manner  in 
contact  with  bases,  that  is,  with  metallic  oxides  or  hydrates. 

1.  If  hydrochloric  acid  be  gradually  added  to  a  concentrated 
solution  of  potassium  hydrate,   the    liquid   becomes  heated, 
and,  as  it  is  neutralized  by  the  acid,  a  white  crystalline  de- 
posit  separates   and   augments   on  cooling:    it  is  potassium 
chloride. 

2.  If  sulphuric  acid  diluted  with  its  volume  of  water  be 
cautiously  and  gradually  added  to  a  concentrated  solution  of 
potassium  hydrate,  the  liquid  becomes  heated,  and,  as  it  is 
neutralized  by  the  acid,  a  white  crystalline  deposit  separates 
and  increases  on  cooling :  it  is  potassium  sulphate. 

The  analogy  between  the  two  reactions  is  marked.  In  each 
case  a  powerful  base,  potassium  hydrate,  has  been  neutralized 
by  an  energetic  acid ;  the  reaction  has  been  accompanied  by 
the  production  of  heat,  and  has  given  rise  to  the  formation 
of  a  saline  matter  which  has  been  deposited.  The  part  of  the 
reaction  which  is  invisible  is  the  formation  of  water.  This 
formation  of  water,  which  always  accompanies  the  generation 


SALTS.  251 

of  a  salt  in  the  ordinary  manners,  is  expressed  in  the  following 
equations : 

KOH       +     HC1    =      KC1       +     H20 

Potassium  hydrate.  Potassium  chloride. 

2KOH  +  H2SO*    =       K2SO       +  2H20 

Potassium  sulphate. 

These  reactions,  it  will  be  seen,  consist  in  an  interchange  of 
elements,  a  double  decomposition.  The  hydrogen  of  the  acid 
is  exchanged  for  the  metal  of  the  potassium  hydrate  and  by 
the  exchange  the  potassium  hydrate  is  converted  into  water, 
while  the  acid,  that  is,  the  salt  of  hydrogen,  is  converted  into  a 
salt  of  potassium.  All  hydrogen  compounds  capable  of  thus 
exchanging  their  hydrogen  for  an  equivalent  quantity  of  metal, 
fill  the  functions  of  acids,  and  these  acids  become  salts  when 
their  hydrogen  is  thus  replaced  by  a  metal.  It  may  then  be 
seen  what  an  important  part  hydrogen  plays  in  the  formation 
of  salts.  From  whence  comes  this  property,  this  capacity  for 
guch  exchanges,  and  of  replacement  by  metals  ?  Without 
doubt  from  the  element  or  group  with  which  the  hydrogen  is 
united  in  the  acids ;  and  in  this  respect  chlorine  and  sulphur 
play  the  same  parts  in  hydrochloric  and  siilphydric  acids  that 
the  oxidized  groups  play  in  nitric,  sulpliuric,  and  phosphoric 
acids. 

HC1  H2S 

H3rdrochloric  acid.          Sulphydric  acid. 

H(N03)  H2(S03)  H3(P03) 

Nitric  acid.  Sulphurous  acid.        Phosphorous  acid. 

H(C103)  H2(S04)  H3(P04) 

Chloric  acid.  Sulphuric  acid.  Phosphoric  acid. 

This  property  is  characterized  by  saying  that  the  elements  or 
groups,  to  which  the  hydrogen  is  united,  are  strongly  electro- 
negative, or  acid,  in  opposition  to  the  hydrogen,  which  is 
strongly  electro-positive,  or  basic. 

When  such  an  acid  reacts  upon  an  oxide,  or  upon  a  hydrate, 
an  interchange  of  elements  takes  place,  and  a  salt  and  water 
are  formed ;  the  latter  is  a  constant  product  necessary  to  the 
reaction.  Other  examples  may  be  added  to  those  already  given. 

If  a  current  of  hydrogen  sulphide  be  passed  into  a  solution 
of  potassium  hydrate  until  no  more  is  absorbed,  potassium 
sulphydrate  and  water  are  formed. 

H2S  +  KOH  =        KSH         +  H20 

Potassium  sulphydrate. 


252  ELEMENTS   OF   MODERN   CHEMISTRY. 

If  an  excess  of  dilute  sulphuric  acid  be  poured  into  a  solu- 
tion of  potassium  hydrate,  potassium  acid  sulphate  and  water 
are  formed. 

H2SO  +  KOH  =        KHSO4        +  H20 

Potassium  acid  sulphate. 

Lastly,  if  cupric  oxide  be  heated  with  dilute  sulphuric  acid, 
it  dissolves,  coloring  the  liquid  blue.  Cupric  sulphate  and 
water  are  formed. 

H2S04     -f     CuO    =     CuSO4    -f     H20 

Cupric  oxide.      Cuprio  sulphate. 

Neutral,  Acid,  and  Basic  Salts. — If  the  salts  result  from 
the  substitution  of  the  metals  for  the  basic  hydrogen  of  acids, 
it  is  evident  that  their  composition  must  be  related  to  that  of 
the  acids  from  which  they  are  derived.  We  know  that  the 
latter  contain  one,  two,  or  three  atoms  of  hydrogen,  capable  of 
being  replaced  by  an  equivalent  quantity  of  metal :  they  are 
monobasic,  dibasic,  and  tribasic.  It  is  evident  that  the  salts 
must  present  analogous  differences  in  their  composition,  accord- 
ing as  they  are  derived  from  a  monobasic,  a  dibasic,  or  a  tribasic 
acid. 

A  salt  is  neutral  when  the  basic  hydrogen  has  been  entirely 
replaced  by  an  equivalent  quantity  of  metal.  But  the  substi- 
tution may  be  only  partial,  for  when  an  acid  contains  two  atoms 
of  basic  hydrogen,  only  one  of  these  atoms  may  be  replaced  by 
one  atom  of  metal ;  there  will  then  remain  in  the  salt  thus 
formed  one  atom  of  basic  hydrogen. 

When  an  acid  contains  three  atoms  of  basic  hydrogen,  it 
may  happen  that  only  one  is  replaced  by  one  atom  of  metal ; 
there  will  then  remain  in  the  salt  two  atoms  of  basic  hydrogen ; 
or  it  may  be  that  two  atoms  of  hydrogen  are  replaced  by  an 
equivalent  quantity  of  metal,  and  there  will  then  remain  in  the 
salt  a  single  atom  of  basic  hydrogen. 

Whenever  basic  hydrogen  thus  remains  in  a  salt,  the  satura- 
tion of  the  acid  is  said  to  be  incomplete.  The  salt  formed 
ordinarily  retains  the  characters  of  an  acid;  it  is  an  acid  salt. 
The  following  table  indicates  the  possible  cases  of  complete 
or  incomplete  saturation  which  may  be  presented  by  a  mono- 
basic, a  dibasic,  and  a  tribasic  acid : 

HNO3  H2SO  H3P04 

Nitric  acid.  Sulphuric  acid.  Phosphoric  acid. 


SALTS.  253 


KNO3 


K     ) 

H'j 


Potassium  nitrate.      Potassium  acid  sulphate.     Monopotassium  phosphate. 

K2S04  |2 

Potassium  sulphate.  Dipotassium  phosphate. 

K3P04 

Tripotassium  phosphate. 

Certain  neutral  salts  possess  the  property  of  combining  with 
the  hydrates  or  the  oxides.  The  compounds  so  formed  contain 
all  of  the  elements  of  the  neutral  salt,  plus  those  of  the  hydrate 
or  oxide;  they  are  called  basic  salts.  Thus,  the  oxides  of 
lead  and  copper  may  combine  with  the  various  salts  of  lead  and 
copper,  forming  basic  salts  of  those  metals. 

Richter's  Laws. — Towards  the  close  of  the  last  century 
fruitful  investigation  was  made  into  the  phenomena  of  neu- 
tralization or  saturation  of  acids  by  bases.  We  know  that  a 
given  weight  of  acid  requires  for  its  neutralization  a  fixed  and 
absolutely  invariable  quantity  of  a  given  base.  Thus,  for  the 
conversion  of  1000  grammes  of  sulphuric  acid  into  neutral 
potassium  salt,  a  quantity  of  potassium  hydrate  corresponding 
to  961  grammes  of  potassium  oxide,  K20,  is  required.  To 
saturate  these  1000  grammes  of  sulphuric  acid,  it  is  necessary 
to  take  weights  of  the  oxides  which  are  invariable  for  each  one 
separately,  but  which  vary  among  themselves. 

Thus,  1000  grammes  of  concentrated  sulphuric  acid  are  neu- 
tralized by  the  following  quantities  of  the  oxides  named  : 

Potassium  oxide 961  grammes. 

Sodium  oxide 632  " 

Barium  oxide 1561  " 

Calcium  oxide 571  " 

Zinc  oxide 866  " 

Cupric  oxide 811  " 

Mercuric  oxide 2204  " 

Silver  oxide 2367  " 

Again,  to  neutralize  1000  grammes  of  the  most  concentrated 
nitric  acid,  the  following  quantities  of  the  same  oxides  are 
required : 

Potassium  oxide 747  grammes. 

Sodium  oxide 492         " 

Barium  oxide .     1214         " 

Calcium  oxide 444         " 

Zinc  oxide 651         " 

Cupric  oxide 631         " 

Mercuric  oxide 1714         " 

Silver  oxide 1841         " 

22 


254  ELEMENTS   OF   MODERN   CHEMISTRY. 

Eichter  was  the  first  to  remark  that  these  latter  quantities 
are  precisely  in  the  same  ratio  to  each  other  as  the  quantities 
of  oxides  which  neutralize  1000  grammes  of  sulphuric  acid. 
Thus, 

961  ^  747 

632  ~~  492 

961  _  747 

1561  ~~12U 

^  _.?!?,  etc. 
571          444 

In  other  words,  the  quantities  of  oxides  which  neutralize  a 
given  weight  of  one  acid  are  proportional  to  the  quantities  of 
the  same  oxides  which  neutralize  the  same  weight  of  another 
acid.  This  law  of  the  composition  of  salts  was  discovered, 
towards  the  close  of  the  last  century,  by  Bichter,  a  chemist  of 
Berlin.  Berzelius  quoted  another  German  chemist,  Wenzel, 
as  the  author  of  this  law  of  proportion,  and  his  error  has 
appeared  in  all  of  the  treatises  on  chemistry  during  the  last 
fifty  years. 

Richter  also  studied  the  phenomenon  of  the  precipitation  of 
metallic  solutions  by  the  metals.  It  is  known  that  when  a 
piece  of  iron  is  plunged  into  a  solution  of  cupric  sulphate,  the 
iron  dissolves,  displacing  a  certain  quantity  of  copper,  without 
other  change.  Since  the  new  salt  formed,  ferrous  sulphate,  ex- 
ists in  the  solution  in  the  same  conditions  of  neutrality  as  the 
cupric  sulphate,  the  quantities  of  metal  which  thus  displace 
each  other  are  equivalent.  As  neither  oxygen  nor  acid  is  set 
at  liberty,  it  must  be  admitted  that  the  respective  quantities  of 
the  metals,  in  the  salts  successively  formed,  are  united  to  the 
same  quantity  of  oxygen,  It  has  even  been  supposed  that  in 
the  salts  which,  like  the  sulphates,  contain  four  atoms  of  oxygen, 
the  metal  is  in  intimate  relation  with  one  of  these  atoms,  which 
is  precisely  sufficient  to  constitute  the  metal  in  the  state  of 
monoxide. 

CuSO4  ==  CuO,S03 
FeSO*  =  FeO,S03 

If  this  were  so,  it  is  evident  that  when  cupric  sulphate  is 
decomposed  by  iron,  the  quantity  of  metal  which  enters  into 
solution  would  combine  or  enter  into  relations  with  precisely  the 
quantity  of  oxygen  abandoned  by  the  copper.  This  quantity  of 
oxygen  being  constant,  the  quantities  of  the  metals  which  com- 


SALTS.  255 

bine  successively  with  it,  differ,  but  are  equivalent  to  each 
other,  and  it  is  evident  that  the  oxides  thus  formed  would  be 
more  rich  in  oxygen  as  the  weight  of  metal  which  enters  into 
solution  is  less  considerable;  in  other  words,  the  richness  of  all 
these  oxides  in  oxygen  is  inversely  proportional  to  the  weights 
of  the  metals  which  successively  become  dissolved ;  it  was  in 
this  form  that  Richter  announced  the  second  law  of  the  com- 
position of  salts.  It  will  be  seen  that  this  law  is  implied  in 
the  first,  and  that  both  are  but  particular  cases  and  natural  con- 
sequences of  the  theory  of  equivalents,  as  it  is  understood  at 
present  and  as  it  has  already  been  explained  (page  23). 

General  Properties  of  Salts. — The  salts  present  very  differ- 
ent colors.  Those  which  are  formed  by  an  acid  possessing  a 
color  are  themselves  colored ;  such  are  the  chromates,  manga- 
nates,  and  permanganates. 

Most  of  the  colored  oxides  form  salts  presenting  various 
colors. 

Ferrous  salts  are  bluish-green. 

Ferric  salts  are  yellow  or  yellowish-brown. 

Manganese  salts  are  rose-colored. 

Chromium  salts  are  dark  green. 

Nickel  salts  are  green. 

Cobalt  salts  are  currant-red  or  blue. 

Cupric  salts  are  blue  or  green. 

Gold  salts  are  yellow. 

It  is  to  be  remarked  that  these  various  colors  are  only  devel- 
oped, as  a  rule,  when  the  salts  are  hydrated,  that  is,  combined 
with  water  of  crystallization.  The  taste  of  the  salts  depends 
upon  their  solubility ;  it  is  wanting  altogether  or  but  slightly 
marked  in  the  insoluble  salts;  more  or  less  pronounced  and 
very  diverse  in  the  soluble  salts.  The  salts  of  magnesium  are 
bitter ;  the  aluminium  salts  are  astringent ;  those  of  iron  astrin- 
gent, with  a  metallic  after-taste ;  the  salts  of  lead  are  at  the 
same  time  sweet  and  astringent ;  the  salts  of  copper,  antimony, 
and  mercury  have  an  acrid  metallic  taste,  which  is  nauseous, 
and  is  called  styptic. 

The  salts  generally  present  regular  forms,  more  frequently 
occurring  in  crystals.  Some  of  them  are  obtained  as  amor- 
phous precipitates,  but  in  nature  even  these  may  assume  the 
crystalline  state. 

Isomorphism. — Certain  salts  which  possess  similar  atomic 
compositions  crystallize  in  identical  or  nearly  identical  forms; 
they  are  called  isomorphom.  It  is  thus  with  the  double  sul- 


256  ELEMENTS    OF    MODERN    CHEMISTRY. 

phates,  which  are  called  alums,  and  of  which  ordinary  alum 
or  aluminium  and  potassium  sulphate  is  the  type.  These  alums 
are  formed  by  the  union  of  a  sulphate,  R2(SO*)3,  with  a  sul- 
phate, M2SO*,  and  they  all  contain  24  molecules  of  water  of 
crystallization. 

Thus,  ordinary  alum, 

A12(S04/.K2SO*    +     24H20 

Aluminium  and  potassium  double  sulphate. 

is  isomorphous  with  chrome  alum  and  iron  alum. 
Cr2(S04)3.K2SO     +     24H20 

Chromium  and  potassium  double  sulphate. 

Fe2(SO4)3.K'S04     +     24H2O 

Iron  and  potassium  double  sulphate. 

All  of  these  alums  crystallize  in  regular  octahedra.  Further, 
a  solution  containing  two  alums,  for  example,  aluminium  and 
potassium  sulphate  and  aluminium  and  ammonium  sulphate, 
deposits  on  concentration  crystals  in  which  the  two  salts  are 
mixed.  Such  is  the  character  of  isomorphous  bodies ;  crystal- 
lizing in  the  same  form,  they  may  mix  together  and  replace 
each  other  in  all  proportions  in  the  same  crystal.  Many  exam- 
ples of  isomorphism  will  be  cited  in  the  course  of  this  work. 
It  will  now  be  sufficient  to  add  that  this  idea  of  isomorphism 
has  rendered  valuable  service  to  chemical  theory  by  permitting 
the  grouping  together  of  bodies  similar  both  in  crystalline  form 
and  atomic  constitution,  and  by  furnishing  in  such  cases  useful 
indications  for  the  determination  of  the  atomic  weights.  It  is 
evident  that  when  two  similar  combinations,  two  sulphates,  for 
example,  are  recognized  to  be  isomorphous,  it  is  necessary  to 
represent  their  constitutions  by  analogous  formulae,  and  the 
latter  can  only  be  possible  under  the  condition  that  the  atomic 
weights  of  the  metals  contained  in  these  sulphates  have  known 
values. 

Action  of  Water  upon  the  Salts. — If  water  be  poured  upon 
and  agitated  with  powdered  chalk,  a  white,  cloudy  liquid  is 
obtained.  The  chalk  is  suspended  in  the  water  without  being 
dissolved ;  it  is  simply  held  up  in  the  form  of  minute  particles, 
and  if  the  liquid  be  allowed  to  stand,  the  precipitate  is  de- 
posited, and  clear  water  again  appears  above  the  deposit. 

However,  if  saltpetre,  or  potassium  nitrate,  be  agitated  with 
water,  a  colorless,  transparent  liquid  is  obtained.  The  saltpetre 
is  dissolved  in  the  water;  it  has  disappeared  as  a  solid  body. 


SALTS.  257 

It  is  melted  by  the  water,  as  is  commonly  said,  and  is  uniformly 
diffused  through  the  liquid.  It  has  itself  become  liquid,  and 
this  is  the  phenomenon  of  solution.  It  is  accompanied  by  a 
production  of  cold,  that  is,  an  absorption  of  heat;  for  in  assum- 
ing the  liquid  state  and  becoming  diffused  throughout  the  water, 
the  saltpetre  must  absorb  heat. 

If  the  introduction  of  powdered  nitre  into  the  solution  be 
continued,  the  solid  still  disappears,  but  a  time  arrives  when 
the  salt  introduced  ceases  to  dissolve ;  for  water  at  a  given  tem- 
perature can  only  dissolve  a  fixed  quantity  of  a  salt,  and  when 
this  limit  is  attained,  the  solvent  force  of  the  water  upon  the  salt- 
petre is  exhausted.  The  water  is  then  said  to  be  saturated  with 
the  salt,  and  any  excess  of  the  latter  remains  in  the  solid  state. 

But  if  now  the  solution  be  heated,  this  excess  is  in  its  turn 
dissolved,  for  the  solubility  augments  with  the  temperature, 
and  as  the  latter  is  elevated,  a  larger  quantity  of  the  salt  is  dis- 
solved. When  the  liquid  begins  to  boil,  the  temperature  and 
the  solubility  of  the  salt  have  reached  their  extreme  limit. 

If  the  boiling  saturated  solution  be  allowed  to  cool,  it  depos- 
its a  large  portion  of  the  salt  in  the  form  of  crystals.  In  this 
manner  voluminous,  colorless,  and  transparent  prisms  are  ob- 
tained which  fill  the  vessel,  and  which  are  surrounded  by  a 
solution  of  saltpetre,  saturated  at  the  temperature  to  which  the 
liquid  has  been  cooled.  This  liquid  is  called  the  mother-liquor 
of  the  crystals.  It  is  thus  that  soluble  salts  are  crystallized  by 
cooling  their  hot  saturated  solutions. 

Generally  the  same  facts  are  observed  for  other  soluble  salts. 
Their  solubility  increases  with  the  temperature;  there  are, 
however,  some  exceptions  to  this  rule.  Sodium  chloride  is 
not  more  soluble  in  hot  than  in  cold  water,  and  gypsum,  or 
calcium  sulphate,  is  sensibly  more  soluble  in  cold  than  in  hot 
water;  for,  while  500  parts  of  boiling  water  are  requisite  to 
dissolve  one  part  of  gypsum,  only  460  parts  of  cold  water  are 
necessary  to  dissolve  the  same  quantity.  The  maximum  solu- 
bility of  sodium  sulphate  is  between  32  and  33°. 

Crystals  of  nitre  may  be  obtained  by  another  process.  We 
may  expose  the  cold  saturated  solution  to  the  air  at  the  ordi- 
nary temperature,  or,  better  still,  place  it  in  a  bell-jar  over  a 
vessel  containing  sulphuric  acid.  The  water  of  the  solution 
slowly  disappears,  and,  as  it  is  dissipated  in  vapor,  a  portion  of 
the  dissolved  salt  separates  in  the  solid  form.  The  crystals  thus 
formed  by  spontaneous  evaporation  are  generally  very  regular. 

22* 


258  ELEMENTS   OF   MODERN   CHEMISTRY. 

But  water  exerts  another  and  a  different  action  upon  the 
salts. 

Perfectly  dry  cupric  sulphate,  CuSO*,  is  a  white  powder. 
If  water  be  poured  upon  it,  it  becomes  blue  and  dissolves,  com- 
municating to  the  liquid  a  blue  color  and  notably  raising  its 
temperature.  On  evaporation,  this  liquid  deposits  crystals  of 
blue  vitriol,  and  if  these  be  compared  with  the  dry  white  pow- 
der with  which  we  started,  they  will  be  found  to  differ  from  it 
by  the  water  they  contain.  We  have  employed  the  anhydrous 
salt,  and  have  hydrated  it.  In  fact,  the  sulphate,  CuSO4,  has 
absorbed  five  molecules  of  water,  with  which  it  has  combined, 
and  this  combination,  like  all  others,  has  taken  place  with  the 
production  of  heat.  The  water  which  is  thus  absorbed  by  cer- 
tain salts,  and  which  combines  with  them  in  definite  propor- 
tions, is  necessary  to  the  formation  of  their  crystals ;  it  is  called 
water  of  crystallization. 

It  is  not  necessary  to  the  constitution  of  the  salts  them- 
selves; they  can  exist  without  it,  and  generally  lose  it  when 
they  are  heated  to  a  temperature  more  or  less  elevated,  without 
undergoing  any  other  decomposition.  Certain  salts  abandon 
their  water  of  crystallization  with  such  facility  that  they  give 
it  up  to  the  surrounding  air  when  the  latter  is  not  saturated 
with  moisture.  They  then  become  opaque  and  lose  their 
forms,  for  crystals  cease  to  exist  when  their  water  of  crystalli- 
zation is  disengaged.  These  salts  become  covered  with  a  dry 
powder  in  the  air  and  are  called  efflorescent  salts. 

It  is  seen  by  the  example  just  cited  that  the  phenomenon 
of  solution  of  salts  in  water,  which  depends  upon  a  physical 
action,  upon  a  change  of  state,  is  often  complicated  with  a  true 
combination  of  the  salt  with  water,  that  is,  a  chemical  action 
which  disengages  heat.  The  latter  is  generally  more  energetic 
than  the  physical  action,  and  the  difference  between  the  two 
effects  is  then  manifested  by  an  elevation  of  temperature. 

But  the  physical  phenomenon  is  produced  alone  when  the 
salt  which  dissolves  is  incapable  of  combining  with  water  of 
crystallization.  A  depression  of  temperature  is  then  observed, 
as  we  have  seen  in  the  case  of  nitre,  the  crystals  of  which  are 
anhydrous;  but  another  example  will  more  clearly  illustrate 
this  important  phenomenon. 

If  water  be  poured  upon  recently  fused  and  powdered  calcium 
chloride,  the  salt  dissolves  with  production  of  heat.  It  changes 
not  only  its  state  but  its  composition ;  it  combines  energetically 


SALTS. 


259 


with  the  water,  and  this  combination  produces  more  heat  than 
is  absorbed  by  the  change  of  state.  Hence  there  is  an  eleva- 
tion of  temperature. 

If  calcium  chloride,  combined  with  its  water  of  crystalliza- 
tion, be  rapidly  mixed  with  snow,  the  salt  is  so  soluble  in  water 
that  it  causes  the  snow  to  melt  at  the  same  time  that  it  becomes 
liquid  itself.  Here  there  is  no  combination,  no  chemical  action, 
and  no  heat  is  disengaged.  It  is  a  double  physical  phenome- 
non,— fusion  of  the  snow  and  fusion  of  the  calcium  chloride, — 
and  neither  of  these  bodies  can  undergo  a  change  of  state  with- 
out absorbing  heat.  Hence  there  is  a  depression  of  tempera- 
ture which  may  reach  — 40°. 

A  mixture  of  snow  and  calcium  chloride  is  a  freezing  mix- 
ture. A  mixture  of  equal  parts  of  common  salt  and  broken 
ice  or  snow  is  frequently  used  for  the  production  of  cold. 

The  phenomenon  of  the  solution  of  salts  in  water  presents 
none  of  the  characteristics  of  a  chemical  action ;  it  does  not 
take  place  in  definite  proportions. 

In  fact,  a  soluble  salt  requires  for  its  complete  solution  a 
quantity  of  water,  which  is  always  the  same  for  a  certain  weight 
of  the  salt  at  a  given  temperature ;  but  there  exists  no  atomic 
relation  between  this  quantity  of  water  and  the  weight  of  the 
salt  which  is  dissolved. 

Further,  although  the  solubility  of  a  salt  presents  for  each 
temperature  a  maximum  limit,  that  is,  although  a  given  weight 
of  a  salt  requires  for  its  solution  a  quantity  of  water  which  is 
invariable  and  which  cannot  be  diminished,  when  the  solution 
has  been  accomplished  an  indefinite  quantity  of  water  may  be 
added,  and  the  liquid  will  still  remain  perfectly  homogeneous. 

Supersaturation, — We  have  seen  that  a  saturated  solution 
of  a  salt  at  a  given  temperature  generally  deposits  a  part  of 
that  salt  on  cooling.  This  is  not  always  the  case  ;  it  sometimes 
happens,  if  the  cooling  take  place  under  certain  conditions,  that 
a  portion  of  the  salt,  which  the  difference  in  temperature  should 
reduce  to  the  solid  state,  still  remains  in  solution.  The  solu- 
tion is  then  said  to  be  supersaturated.  Sodium  sulphate  and 
alum  have  a  great  tendency  to  form  such  solutions. 

A  hot,  saturated  solution  of  sodium  sulphate  is  contained  in 
the  tube  A  (Fig.  95).  It  is  heated  to  boiling,  so  that  the  vapor 
escapes  by  the  drawn-out  extremity.  By  the  aid  of  a  blow- 
pipe, the  tube  is  then  sealed  at  C,  before  the  vapor  can  con- 
dense, and  is  then  allowed  to  cool.  A  vacuum  is  formed  above 


260  ELEMENTS   OF    MODERN    CHEMISTRY. 

the  solution,  for  the  air  has  been  driven  out  by  the  vapor.  The 
cold  liquid  remains  limpid ;  it  deposits  no  crystals.  But  the 
instant  the  drawn-out  point  of  the  tube  is  broken  off,  the  air 
enters  and  crystallization  at  once  commences  at  the  surface  and 


FIG.  95. 

proceeds  throughout  the  entire  mass,  which  becomes  solid ;  at 
the  same  time  an  elevation  of  temperature  may  be  observed. 

100  grammes  of  water  and  200  grammes  of  crystallized  so- 
dium sulphate  may  be  heated  to  ebullition  in  a  narrow-necked 
flask,  and  as  sooft  as  vapor  begins  to  issue  from  the  mouth,  the 
latter  may  be  covered  with  a  watch-glass  and  the  whole  allowed 
to  cool  tranquilly.  The  salt  remains  dissolved,  and  the  solution 
contained  in  the  flask  is  supersaturated;  but  as  soon  as  the 
watch-glass  is  removed  the  liquid  becomes  a  solid  mass  of  crys- 
tals (Loewel). 

In  the  first  experiment  it  is  the  sudden  entry  of  the  air 
which  determines  the  crystallization ;  in  the  second,  it  is  the 
free  access  of  air,  and  it  may  be  admitted  that  in  each  case  the 
air  acts  by  the  corpuscles  which  it  holds  in  suspension,  and 
which,  falling  into  the  solution,  determine  the  crystallization. 
Indeed,  Loewel  has  shown  that  air  which  has  been  filtered 


SALTS.  261 

through  cotton-wool  has  lost  the  property  of  causing  supersat- 
urated solutions  to  crystallize. 

But  what  is  the  nature  of  these  particles  which  by  falling 
upon  the  surface  of  supersaturated  solutions  occasion  crystalli- 
zation ?  The  researches  of  Gernez  have  thrown  great  light  upon 
this  question.  According  to  him,  they  are  saline  particles  simi- 
lar to  the  salt  dissolved.  The  sodium  sulphate  is  deposited  in 
the  preceding  experiments  because  the  entry  of  the  air  has 
allowed  an  imperceptible  particle  of  sodium  sulphate  to  fall 
upon  the  surface  of  the  liquid,  and  around  this  particle  the 
crystallization  "begins  immediately  and  is  propagated  through- 
out the  entire  mass  of  the  supersaturated  liquid.  The  air  then 
contains  a  trace  of  sodium  sulphate,  as  it  contains  a  trace  of 
common  salt  and  of  carbonate  and  sulphate  of  calcium.  These 
particles  are  suspended  in  the  air  in  a  state  of  extreme  division, 
and  are  carried  from  great  distances  by  the  winds. 

A  boiling  saturated  solution  of  sodium  hyposulphite  may  be 
allowed  to  cool  in  a  carefully-corked  flask.  When  cold,  it  is  so 
concentrated  that  it  possesses  an  oily  consistency.  The  flask 
may  be  carefully  uncorked  and  the  surface  of  the  liquid  touched 
with  a  rod  to  the  end  of  which  a  small  particle  of  sodium  hy- 
posulphite has  been  made  to  adhere.  Crystallization  at  once 
commences  at  the  spot  where  the  rod  touches  the  liquid,  and 
in  a  few  seconds  the  whole  mass  becomes  solid.  There  is  at 
the  same  time  a  notable  disengagement  of  heat  (Gernez). 

The  crystallization  will  also  take  place  if  a  particle  of  sodium 
sulphate  be  allowed  to  fall  into  the  solution,  for  the  latter  salt 
possesses  the  same  crystalline  form  as  sodium  hyposulphite,  and 
an  analogous  constitution. 

Ebullition  of  Saline  Solutions. — Aqueous  solutions  of  the 
salts  generally  possess  a  boiling-point  higher  than  that  of  water. 
Thus,  a  saturated  solution  of  common  salt  boils  at  108.4° ;  a 
saturated  solution  of  potassium  nitrate  boils  at  115.9°;  and  a 
saturated  solution  of  calcium  chloride  boils  only  at  1*79.5°. 

Action  of  Heat  upon  the  Salts. — The  hydrated  salts  lose 
their  water  when  they  are  heated.  Ordinarily,  a  temperature 
of  100°  is  sufficient  to  expel  the  water  of  crystallization.  Cer- 
tain salts  melt  in  this  water  before  losing  it ;  they  are  so  soluble 
in  hot  water  that  they  dissolve  in  the  water  which  at  a  lower  tem- 
perature constitutes  them  in  the  crystalline  state.  This  is  called 
aqueous  fusion.  A  great  number  of  anhydrous  salts  melt  when 
they  are  exposed  to  intense  heat;  this  is  called  igneous  fusion. 


262 


ELEMENTS   OF   MODERN   CHEMISTRY. 


Heat  exerts  a  decomposing  action  upon  many  salts.  Upon 
this  point  it  is  difficult  to  give  general  laws.  It  can  only  be 
said  that  the  stability  of  a  salt  depends  upon  three  conditions, 
namely,  the  fixedness  of  the  corresponding  acid,  the  stability 
of  the  corresponding  oxide,  and  the  energy  of  the  affinity  with 
which  the  two  react  together  to  form  the  salt. 

Thus  the  salts  of  acids  decomposable  by  heat  are  themselves 
decomposed  at  an  elevated  temperature.  It  is  thus  with  the 
chlorates,  the  perchlorates,  and  the  nitrates.  Among  the  sul- 
phates, some  are  decomposable,  others  are  fixed.  The  latter  are 
those  of  potassium,  sodium,  barium,  strontium,  calcium,  mag- 
nesium, lead,  etc.  The  corresponding  oxides  of  potassium, 
sodium,  barium,  etc.,  are  fixed  bases,  and  possess  a  powerful 
affinity  for  sulphuric  acid.  Hence  their  sulphates  are  stable. 

Most  of  the  carbonates  are  decomposable  by  heat;  indeed, 
the  affinity  of  carbonic  acid  for  the  bases  is  as  a  rule  feeble. 
It  is  exceptionally  strong  for  the  alkaline  bases  ;  hence  the  alka- 
line carbonates  and  barium  carbonate  resist  the  action  of  heat. 
Action  of  Electricity  upon  the  Salts.— When  an  electric 

current  traverses  the  aque- 
ous solution  of  a  salt,  the 
latter  is  decomposed.  The 
metal  separates  at  the  neg- 
ative pole,  and  the  other 
element  of  the  salt  at  the 
positive  pole.  This  other 
element  may  be  an  elec- 
tro-negative element,  such 
as  chlorine,  or  an  oxidized 
group,  that  is,  a  group  of 
atoms,  one  or  more  of 
which  is  oxygen. 

The  electrolysis  of  a 
salt  may  be  effected  as 
follows:  An  U  tube  (Fig. 
96)  contains  a  solution  of 
cupric  chloride.  In  each 
branch  a  plate  of  platinum 
dips  into  the  liquid,  and 
these  plates,  connected  by 


FIG.  96. 

conducting  wires  with  the  two  poles  of  a  battery,  constitute 
the  positive  and  negative  electrodes. 


As  soon  as  the  current 


SALTS.  263 

passes,  the  electro-positive  element  of  the  salt,  the  copper,  is 
deposited  upon  the  electro-negative  electrode,  and  the  chlorine, 
which  is  electro-negative,  is  disengaged  at  the  positive  electrode. 
A  part  of  this  chlorine  combines  with  the  platinum  electrode 
by  a  secondary  reaction,  forming  platinum  chloride,  but  the 
principal  action,  that  is,  the  decomposition  of  cupric  chloride 
by  electrolysis,  is  represented  by  the  following  equation: 

Cuci2  =   Cu   +   CP 

Cupric  chloride.        Copper.  Chlorine. 

If  the  cupric  chloride  be  replaced  by  cupric  sulphate,  the 
current  will  decompose  this  salt  into  copper,  which  deposits 
upon  the  negative  electrode,  and  into  SO*,  which  possesses  no 
stability,  and  consequently  breaks  up  at  the  positive  electrode 
into  SO3,  which  combines  with  the  water  to  form  sulphuric 
acid,  and  O,  which  is  disengaged  at  the  positive  electrode. 

The  decomposition  of  the  SO4  is  a  secondary  action.  The 
principal  action  accomplished  by  the  work  of  the  current  is 
expressed  by  the  following  equation : 

CuSO4       =       C+u       +       S~04 

Cupric  sulphate.  Copper.  Oxidized  group. 

The  secondary  reactions  are  as  follows : 

SO4  =  SO3  +  0 
SO3  -f  H20  =  H2S04 

The  experiment  may  be  repeated  upon  potassium  sulphate, 
and  a  solution  of  this  salt  colored  by  the  syrup  of  violets  is  in- 
troduced in  the  U  tube.  As  soon  as  the  current  passes,  bub- 
bles of  gas  are  seen  to  arise  from  each  electrode.  Free  oxygen 
appears  at  the  positive  electrode,  as  in  the  preceding  case,  and 
at  the  same  time  the  liquid  filling  this  branch  of  the  tube  as- 
sumes a  red  color.  This  is  the  evidence  of  the  presence  of 
sulphuric  acid  formed  at  the  positive  electrode. 

The  gas  disengaged  at  the  negative  electrode  is  hydrogen, 
which  is  produced  by  a  secondary  action  of  the  water  upon  the 
potassium  which  is  removed  from  the  salt  at  the  negative  pole. 
Potassium  hydrate  is  thus  formed,  and  the  syrup  of  violets 
in  this  branch  of  the  tube  is  colored  green.  The  principal  ac- 
tion accomplished  by  the  current  is  expressed,  as  in  the  pre- 
ceding cases,  by  the  equation 

K2S04       =      K8       +       SO* 

Potassium  sulphate.        Potassium.          Oxidized  group. 


264  ELEMENTS   OF   MODERN   CHEMISTRY. 

The  metal,  which  is  electro-positive,  is  carried  to  the  nega- 
tive pole ;  the  oxidized  group  to  the  positive  pole.  But  the 
two  elements  thus  separated  have  provoked  or  undergone  sec- 
ondary actions  independent  of  the  work  of  the  current.  The 
potassium  has  decomposed  the  water,  the  oxidized  group  has 
been  broken  up,  as  explained  in  the  preceding  case. 

It  will  be  understood  from  these  reactions  that  all  of  the 
salts,  whatever  may  be  their  nature,  undergo  the  same  kind  of 
decomposition  when  submitted  to  the  action  of  an  electric  cur- 
rent. They  are  separated  into  two  elements.  The  one  is  elec- 
tro-positive, and  is  liberated  at  the  negative  pole ;  this  is  always 
the  metal.  The  other  is  electro-negative  and  goes  to  the  posi- 
tive pole,  whether  it  be  a  simple  body,  such  as  chlorine,  or  an 
oxidized  group,  such  as  SO4*  It  will  also  be  seen  that  such 
groups  occupy  in  the  oxidized  salts  the  same  position  held  by 
chlorine  in  the  chlorides.  Such  is  the  principal  action,  that  is, 
the  decomposition,  accomplished  by  the  action  of  the  electric 
current,  a  decomposition  which  is  called  electrolysis. 

Action  of  the  Metals  upon  the  Salts. — The  metals  may 
displace  each  other  in  their  saline  solutions. 

If  a  plate  of  copper  be  plunged  into  a  solution  of  silver 
nitrate,  the  copper  enters  into  solution  in  the  form  of  cupric 
nitrate,  displacing  and  precipitating  the  silver. 

Cu     -f     2AgN03     =     Cu(N03)2     +     Ag2 

Silver  nitrate.  Cupric  nitrate. 

If  a  piece  of  iron  be  introduced  into  a  solution  of  cupric 
sulphate,  the  iron  instantly  becomes  covered  with  a  layer  of 
metallic  copper,  precipitated  by  a  portion  of  the  iron  which 
enters  the  solution. 

Fe     -f     CuSO4      ==    Cn    +      FeSO4 

Cnpric  sulphate.  Ferrous  sulphate. 

If  a  strip  of  zinc  around  which  some  brass  wires  have  been 
twisted  be  suspended  in  a  dilute  solution  of  plumbic  acetate, 
the  zinc  will  slowly  displace  the  lead,  which  will  be  deposited 
in  brilliant  scales  upon  the  brass  wires.  The  latter  gradually 
assume  the  appearance  of  fern-leaves,  and  the  experiment 
constitutes  the  formation  of  the  lead-tree. 

Richter,  of  Berlin,  was  the  first  to  remark  (1792)  that  the 
metals  displace  each  other  in  their  saline  solutions  without  the 
neutrality  of  the  latter  being  disturbed.  When  a  neutral  salt 
is  precipitated  by  a  metal,  a  new  neutral  salt  results.  The 


BERTHOLLET  S   LAWS. 


265 


ferrous  sulphate  formed  by  the  action  of  iron  upon  cupric  sul- 
phate is  neutral  like  the  latter. 

It  may  be  further  stated  that  in  this  respect  the  chlorides 
behave  like  the  oxygen  salts.  Iron  displaces  copper  from  cu- 
pric chloride  as  from  the  sulphate.  In  the  first  case  it  com- 
bines with  CP,  in  the  second  with  SO4,  and  in  this  circumstance 
again  the  latter  group  acts  in  the  same  manner  as  chlorine. 

CuCP      +      Fe      =      FeCP      +      Cu 

Cupric  chloride.  Ferrous  chloride. 

Cu(S04)     +     Fe     =     Fe(S04)     +     Cu 

Cupric  sulphate.  Ferrous  sulphate. 

The  following  table  indicates  the  order  in  which  the  metals 
precipitate  saline  solutions : 


SALTS   OF   WHICH   THE    METALS   ARE   PRECIPITATED   BY 
CERTAIN    METALS. 


Salts  of  tin    .     . 
Salts  of  antimony 
Salts  of  bismuth 
Salts  of  lead      . 
Salts  of  copper  . 

Salts  of  mercury 


Salts  of  silver    . 
Salts  of  platinum 
Salts  of  gold  .     . 


reduced  by  iron,  zinc, 
and  all  the  preceding 
metals 

reduced  by  iron,  zinc, 
manganese,  cobalt, 
and  all  the  preceding 
metals 


reduced  by  iron  and  zinc. 


BERTHOLLET'S   LAWS. 

To  conclude  this  general  study  of  the  salts,  it  only  remains 
to  indicate  the  actions  exerted  upon  them  by  the  acids  and  the 
bases,  and  the  reciprocal  actions  of  the  salts  themselves.  These 
facts  have  been  established  and  discussed  principally  by  Ber- 
thollet,  who  demonstrated  the  influence  of  physical  conditions, 
such  as  insolubility  and  volatility,  upon  the  direction  of  chem- 
ical decompositions. 

Action  of  Acids  upon  the  Salts. — When  an  acid,  that  is,  a 
salt  of  hydrogen,  is  added  to  a  metallic  salt,  the  former  tends 
to  exchange  elements  with  the  latter,  in  such  a  manner  as  to 
form  a  new  salt  and  a  new  acid. 

If  sulphuric  acid  be  added  to  powdered  potassium  nitrate, 
M  23 


266  ELEMENTS   OF   MODERN   CHEMISTRY. 

the   latter  partially  dissolves  without  the  aid  of  heat,   and 
potassium  acid  sulphate  and  nitric  acid  are  formed. 

KNO3     +      H2SO*     =     HNO3      -f      KHSO4 

Potassium  nitrate.         Sulphuric  acid.  Nitric  acid.     Potassium  acid  sulphate. 

But  this  reaction  is  by  no  means  complete.  Powerful  as 
are  its  affinities,  the  sulphuric  acid  cannot  decompose  the  whole 
of  the  potassium  nitrate  unaided  by  heat ;  a  portion  of  the  latter 
salt  remains  unaltered  in  presence  of  the  excess  of  sulphuric 
acid,  so  that  the  resulting  thick  and  fuming  liquid  really  con- 
tains two  acids  and  two  salts,  namely : 

Sulphuric  acid. 
Nitric  acid. 

Potassium  acid  sulphate. 
Potassium  nitrate. 

The  reaction  takes  place  as  if  two  acids  were  in  presence  of 
a  single  base.  There  is  a  conflict  between  the  acids,  and  they 
tend  to  divide  the  base,  which  is  potassium,  in  such  a  manner 
that  each  acid  may  saturate  a  portion. 

Hence  the  decomposition  of  potassium  nitrate  is  not  com- 
plete, and  it  is  arrested  as  soon  as  the  nitric  acid  set  free  can 
dispute  with  the  sulphuric  acid  the  possession  of  the  base. 
There  is  then  established  a  state  of  equilibrium  between  the 
two  acids,  both  remaining  in  presence  of  the  two  salts. 

But  this  equilibrium  is  unstable  and  may  be  deranged  by 
various  circumstances. 

If  the  acid  mixture  be  heated,  abundant  white  vapors  are 
disengaged.  It  is  the  nitric  acid  which  volatilizes.  But  the 
sulphuric  acid  becomes  thus  preponderant  in  the  liquid  and 
decomposes  another  portion  of  potassium  nitrate,  and,  if  the 
volatilization  of  the  nitric  acid  set  free  be  not  arrested  by  the 
removal  of  the  heat,  it  is  evident  that  nothing  can  prevent  the 
complete  decomposition  of  the  potassium  nitrate  by  the  sul- 
phuric acid.  The  nitric  acid,  which  by  its  presence  alone 
prevented  this  total  decomposition,  is  rendered  powerless. 

Such  is  the  influence  of  volatility  or  the  gaseous  state  upon 
the  progress  of  decompositions ;  it  is  manifested  in  the  highest 
degree  in  acids  more  volatile  than  nitric  acid,  such  as  carbonic 
and  sulphurous  acids.  We  have  already  seen  that  the  carbon- 
ates and  sulphites  are  easily  and  entirely  decomposed  by  the 
energetic  acids. 

While  the  volatility  of  acids  favors  the  decomposition  of 
their  salts,  insolubility  may  play  an  analogous  part. 


BERTHOLLET'S  LAWS.  26*7 

If  hydrochloric  acid  be  added  to  a  solution  of  potassium  sili- 
cate, a  gelatinous  precipitate  of  silicic  acid  is  at  once  produced, 
and  at  the  same  time  potassium  chloride  is  formed.  The  de- 
composition is  complete,  for  the  silicic  acid  is  insoluble. 

If  sulphuric  acid  be  poured  into  a  solution  of  barium  nitrate, 
a  precipitate  of  barium  sulphate  is  immediately  formed,  while 
at  the  same  time  nitric  acid  is  set  free. 

Ba(N03)2     -f     H2SO     =     2HN03     +     BaSO 

Barium  nitrate.          Sulphuric  acid.  Nitric  acid.         Barium  sulphate. 

In  this  case  also  the  decomposition  is  complete,  for  the  ba- 
rium sulphate  is  insoluble. 

In  these  two  reactions,  the  division  of  the  base  between  the 
two  acids  cannot  take  place,  since  one  of  the  products  is  imme- 
diately removed  from  the  sphere  of  action  by  its  insolubility. 
In  the  first  case,  it  is  the  newly-formed  acid  which  is  precipi- 
tated ;  in  the  second,  it  is  the  newly-formed  salt  which  is  de- 
posited in  the  insoluble  state. 

Influence  of  Mass. — One  other  circumstance  can  influence 
the  extent  of  these  decompositions :  it  is  the  relative  masses  of 
the  bodies  which  are  in  presence  of  each  other. 

In  the  first  experiment,  it  was  supposed  that  an  amount  of 
sulphuric  acid  had  been  added  to  potassium  nitrate  sufficient  to 
produce  the  double  decomposition.  If  a  large  excess  had  been 
employed,  it  is  evident  that  it  would  have  become  preponderant 
in  the  mixture,  and  that  it  would  have  displaced  a  more  con- 
siderable portion  of  nitric  acid. 

The  influence  of  mass  is  manifested  in  the  case  of  very  feeble 
acids,  and  permits  them  to  displace  stronger  acids.  If  a  small 
quantity  of  tricalcic  phosphate  be  introduced  into  water  charged 
with  carbonic  acid,  the  latter,  compensating  by  its  mass  for  its 
deficiency  in  energy,  will  remove  from  the  phosphate  a  portion 
of  its  base.  Calcium  dicarbonate  and  calcium  acid  phosphate 
are  formed,  both  of  which  are  soluble. 

Such,  according  to  Berthollct,  is  the  influence  of  insolubility 
and  volatility  upon  the  phenomena  of  double  decomposition ; 
such,  on  the  other  hand,  is  the  influence  of  mass.  The  same 
conditions  intervene,  and  in  the  same  manner,  in  the  reactions 
which  we  are  about  to  study. 

Action  of  Bases  upon  the  Salts. — We  will  here  consider 
only  the  action  of  the  soluble  bases,  that  is,  the  alkaline  hy- 
drates. 


268  ELEMENTS   OF   MODERN   CHEMISTRY. 

If  a  solution  of  potassium  hydrate  be  poured  into  a  solu- 
tion of  sodium  sulphate,  no  apparent  change  takes  place ;  but, 
according  to  the  principle  which  has  just  been  announced,  it  is 
probable  that  the  potassium  hydrate  has  liberated  a  portion 
of  sodium  hydrate. 

Na2S04      +     2KOH       =      K2S04      +      2NaOH 

Sodium  sulphate.    Potassium  hydrate.      Potassium  sulphate.      Sodium  hydrate. 

But  this  decomposition  cannot  be  complete,  and  the  liquid 
must  contain  four  bodies,  namely : 

Sodium  sulphate. 
Potassium  sulphate. 
Sodium  hydrate. 
Potassium  hydrate. 

If  potassium  hydrate  be  added  to  a  solution  of  cupric  sul- 
phate, a  light-blue  precipitate  of  cupric  hydrate  is  obtained. 
In  this  case  the  decomposition  is  complete,  owing  to  the  insol- 
ubility of  the  cupric  hydrate  which  cannot  dispute  with  the 
potassium  hydrate  the  possession  of  the  acid. 

CuSO4     +      2KOH     =     K2S04     +      Cu(OH)2 

Cupric  sulphato.      Potassium  hydrate..    Potassium  sulphate.        Cupric  hydrate. 

If  a  solution  of  barium  hydrate  be  poured  into  a  solution  of 
potassium  sulphate,  a  precipitate  of  barium  sulphate  is  pro- 
duced, and  potassium  hydrate  remains  in  solution.  In  this 
case  again,  the  decomposition  is  complete,  by  reason  of  the  in- 
solubility of  the  barium  sulphate.  The  potassium  cannot  di- 
vide the  acid  with  the  barium,  for  the  latter  escapes  with  all 
of  it  in  the  form  of  insoluble  sulphate. 

K2S04       +    Ba(OH)2     =      BaSO4     -f      2KOH 

Potassium  sulphate.        Barium  hydrate.        Barium  sulphate.      Potassium  hydrate. 

Action  of  the  Salts  upon  each  other. — The  action  of  salts 
upon  each  other  is  what  would  naturally  follow  from  the  prin- 
ciples exposed  in  treating  of  the  action  of  acids  upon  salts. 
Indeed,  the  latter  possess  the  same  constitution  as  the  acids, 
and  in  their  reactions  upon  salts  should  give  rise  to  phenomena 
of  the  same  order.  These  are  exchanges  of  elements,  double 
decompositions,  which  take  place  and  are  more  or  less  complete, 
according  to  the  physical  conditions  of  the  bodies  which  are 
produced,  and  also  according  to  the  relative  masses  of  the  re- 
acting bodies. 

In  the  first  place,  we  must  consider  the  reciprocal  actions  of 
the  soluble  salts. 


BERTHOLLET'S  LAWS.  269 

If  a  solution  of  cupric  sulphate  be  treated  with  a  solution 
of  sodium  chloride,  no  precipitate  is  formed,  but  the  blue  color 
of  the  liquid  is  changed  to  green.  This  color  is  that  of  cupric 
chloride,  and  it  may  be  supposed  that  the  latter  salt  is  formed 
by  the  reciprocal  action  of  the  sodium  chloride  and  cupric 
sulphate. 

CuSO4      +      2NaCl      =     Na2S04      +      CuCP 

Cupric  sulphate.        Sodium  chloride.        Sodium  sulphate.        Cupric  chloride. 

But  this  interchange  of  elements  between  the  cupric  sulphate 
and  the  sodium  chloride  is  arrested  before  the  decomposition 
of  the  two  salts  is  complete.  A  part  of  each  remains  unaltered 
in  the  presence  of  the  other  and  of  the  two  new  salts  which 
are  formed.  Consequently,  the  green  liquor  obtained  in  this 
experiment  contains  four  salts,  namely : 

Cupric  sulphate. 
Sodium  chloride. 
Sodium  sulphate. 
Cupric  chloride. 

The  respective  proportions  in  which  these  salts  exist  in  the 
mixture  depend  upon  several  circumstances.  Malaguti  has 
shown  that  in  cases  of  this  kind  it  is  the  energy  of  the  affinity 
of  the  acids  for  the  bases  which  governs  the  decomposition. 
The  most  energetic  acid  tends  to  combine  with  the  most  power- 
ful base,  and  the  proportion  of  the  salt  thus  formed  predomi- 
nates in  the  mixture.  Thus  there  is  set  up,  as  it  were,  between 
the  elements  in  presence  a  sort  of  conflict,  in  which  the  stronger 
are  victorious,  while  the  weaker  are  not  altogether  annihilated. 
The  result  is  a  state  of  equilibrium  which  is  only  disturbed  in 
case  one  of  the  products  is  by  reason  of  its  insolubility  removed 
from  the  sphere  of  action  of  the  other.  The  latter  condition 
is  realized  in  the  following  experiments. 

When  barium  chloride  is  added  to  the  blue  solution  of  cupric 
sulphate,  a  precipitate  of  barium  sulphate  is  immediately  formed, 
and  cupric  chloride  remains  in  solution,  coloring  the  liquid 
green. 

CuSO4     -f     Bad2     =     BaSO4     +     CuCl2 

Cupric  sulphate.   Barium  chloride.    Barium  sulphate.    Cupric  chloride. 

In  this  case  the  decomposition  is  complete,  owing  to  the  in- 
solubility of  the  barium  sulphate.  That  salt  is  removed  by 
cohesion  from  the  sphere  of  action  of  the  compounds  which 
remain  in  solution.  The  portions  first  formed,  and  thus  with- 

23* 


270  ELEMENTS    OF    MODERN    CHEMISTRY. 

drawn,  are  replaced  by  others,  and  the  reaction  once  commenced 
is  finished  in  the  same  manner,  so  that  the  whole  of  the  cupric 
sulphate  is  converted  into  barium  sulphate. 

A  concentrated  solution  of  common  salt  produces  no  precipi- 
tate in  a  concentrated  solution  of  magnesium  sulphate.  How- 
ever, we  must  admit  that  there  is  an  interchange  of  elements, 
and  that  the  liquid  contains  four  salts,  namely : 

Magnesium  sulphate. 
Sodium  chloride. 
Sodium  sulphate. 
Magnesium  chloride. 

If  this  solution  be  exposed  to  an  intense  cold,  it  deposits 
crystals  of  sodium  sulphate,  while  magnesium  chloride  remains 
in  solution  (Balard).  Of  the  four  salts  which  are  in  presence 
of  each  other,  the  sodium  sulphate  is  the  least  soluble ;  it  is 
therefore  deposited,  and  the  double  decomposition  continues 
in  the  same  manner  until  the  greater  part  of  the  magnesium 
sulphate  has  been  decomposed. 

The  subject  could  be  further  developed  by  other  examples. 
Those  which  have  been  given  are  sufficient  to  expose  the  true 
principle  of  double  decomposition. 

We  may  add  that  if  the  operations  be  conducted  in  the  dry 
way  and  at  a  high  temperature,  the  volatility  of  the  products 
which  may  be  formed  exerts  an  influence  upon  the  reactions 
analogous  to  that  which  has  been  established  for  insolubility. 

If  an  intimate  mixture  of  mercuric  sulphate  and  sodium 
chloride  be  heated  in  a  glass  matrass,  a  sublimate  of  mercuric 
chloride  is  formed. 

HgSO4     +     2NaCl     =     Na2S04     +     HgCl2 

Mercuric  sulphate.      Sodium  chloride.    Sodium  sulphate.     Mercuric  chloride. 

Action  of  Soluble  Salts  upon  Insoluble  Salts. — The  study 
of  double  decomposition  may  be  concluded  by  a  summary  ex- 
position of  the  action  of  soluble  salts  upon  insoluble  salts.  It 
is  analogous  to  that  which  has  just  been  studied,  that  is,  it  is 
characterized  by  a  tendency  to  an  interchange  of  elements.  A 
single  example  will  be  sufficient. 

If  a  solution  of  sodium  carbonate  be  boiled  for  a  long  time 
with  barium  sulphate,  it  is  found  that  the  latter  salt  has  under- 
gone a  partial  decomposition.  It  is  partially  converted  into 
barium  carbonate,  insoluble  like  the  sulphate,  and  the  liquid 
becomes  charged  with  a  certain  quantity  of  sodium  sulphate. 
BaSO3  +  Na2C03  =  Na'SO4  +  BaCO4 

Barium  sulphate.      Sodium  carbonate.       Sodium  sulphate.      Barium  carbonate. 


NITRATES.  271 

This  decomposition  is  more  complete  as  the  proportion  of 
sodium  carbonate  which  reacts  upon  the  barium  sulphate  is 
increased.  Here,  as  in  some  of  the  preceding  experiments,  the 
influence  exerted  by  the  greater  mass  is  very  appreciable. 

This  study  may  be  aptly  terminated  by  summary  indications 
upon  the  composition  and  properties  of  the  more  important 
classes  of  salts,  which  are  the  nitrates,  sulphates,  and  carbonates. 

NITRATES. 

Composition.  —  Nitric  acid  containing  HNO3,  the  nitrates 
contain  the  group  NO3  combined  with  a  metal  which  replaces 
the  hydrogen  of  the  acid.  Consequently  they  contain  one  or 
more  groups,  NO3,  according  to  the  nature  of  the  metal  which 
has  neutralized  the  nitric  acid.  Thus, 

1.  KOH    +     HNO3      =    KNO3        +     H20 

Potassium  hydrate.       Nitric  acid.  Potassium  nitrate. 

2.  PbO      +     2HN03     =     Pb(N03)2  +     H20 

Plumbic  oxide.  Plumbic  nitrate. 


3.  03    +    3HN03    =    Bi(N03)3    +    3H20 

Bismuthic  hydrate.  Bismuth  trinitrate. 

With  these  few  examples,  we  may  conclude  : 

1.  That  potassium,  which  unites  with  one  atom  of  chlorine 
to  form  potassium  chloride,  KC1,  unites  also  with  one  group, 
NO3,  to  form  potassium  nitrate. 

2.  That  lead,  which  unites  with  two  atoms  of  chlorine  to 
form  plumbic  chloride,  PbCl2,  unites  also  with  two  groups, 
NO3,  to  form  plumbic  nitrate. 

3.  That  bismuth,  which  unites  with  three  atoms  of  chlorine 
to  form  bismuth  trichloride,  BiCl3,  unites  also  with  three  groups, 
NO3,  to  form  bismuth  trinitrate. 

In  the  chloride  K'Cl  potassium  is  monatomic. 

In  the  chloride  Pb"Cl2  lead  is  diatomic. 

In  the  chloride  Bi'"Cl3  bismuth  is  triatomic. 

In  the  nitrates,  these  three  metals  play  the  same  parts  as  in 
the  chlorides;  and  we  may  say,  in  a  general  manner,  that  the 
metallic  nitrates  contain  a  metal  united  with  as  many  times 
NO3  as  the  metal  possesses  atomicities. 

In  K'(N03)  monatomic  potassium  is  united  with  NO3 

In  Pb"(N03)2  diatomic  lead  is  united  to  2N03 

In  Bi"'(N03)3  triatomic  bismuth  is  united  to  3N03 

Such  is  the  law  of  the  composition  of  the  nitrates. 


272  ELEMENTS   OF   MODERN   CHEMISTRY. 

Properties. — All  of  the  nitrates  are  soluble  in  water.  Some 
of  them  are  deposited  from  their  solutions  in  the  form  of  hy- 
drated  crystals.  Such  is  cupric  nitrate,  which  crystallizes  with 
six  molecules  of  water  at  a  low  temperature. 

Others  separate  in  anhydrous  crystals.  Such  are  the  nitrates 
of  potassium,  sodium,  silver,  barium,  and  lead. 

All  of  the  nitrates  are  decomposable  by  heat,  and  the  pro- 
ducts of  the  decomposition  vary  with  the  nature  of  the  nitrate 
and  with  the  temperature.  Thus,  potassium  nitrate  is  first 
converted  into  nitrite,  and  this  is  finally  decomposed  into 
nitrogen,  oxygen,  and  potassium  oxide.  The  nitrates  of  barium 
and  lead  yield  nitrogen  peroxide,  oxygen,  and  a  residue  of 
oxide.  Silver  nitrate  yields  nitrogen  peroxide,  oxygen,  and  a 
residue  of  metal. 

2AgN03  =  N204  -f  O2  -f  Ag2 

All  of  the  nitrates  liberate  oxygen  when  they  are  heated; 
rich  in  oxygen,  they  constitute  an  abundant  source  of  that 
element,  and  they  are  also  easily  reduced  by  bodies  possessing 
a  strong  affinity  for  it. 

Sulphur,  charcoal,  phosphorus,  and  certain  metals  are  ener- 
getically oxidized  when  heated  with  the  nitrates. 

If  sulphur  be  heated  with  potassium  nitrate,  potassium 
sulphate  is  formed,  and  sulphurous  oxide  and  nitrogen  are 
disengaged. 

2KN03     +     S2    =    K2S04     +     SO2     +     N2 

Potassium  nitrate.  Potassium  sulphate. 

When  powdered  potassium  nitrate  is  thrown  upon  burning 
charcoal,  the  salt  melts  and  increases  the  combustion  of  the 
charcoal,  producing  a  vivid  deflagration.  Potassium  carbonate 
is  formed  and  carbon  dioxide  and  nitrogen  are  disengaged. 

4KN03     +     50     =     2K2C03     +     SCO2     +     2N2 

Potassium  nitrate.  Potassium  carbonate. 

Distinctive  Characters, — All  of  the  nitrates  deflagrate  when 
thrown  upon  incandescent  charcoal. 

With  concentrated  sulphuric  acid  they  evolve  white  vapors  of 
•nitric  acid  in  the  cold,  and  more  abundantly  when  the  reaction 
is  aided  by  heat.  When  mixed  with  copper-filings  and  treated 
with  concentrated  sulphuric  acid,  they  disengage  red  vapors. 

When  the  solution  of  a  nitrate  is  mixed  with  its  own  volume 
of  concentrated  sulphuric  acid,  and  a  crystal  of  ferrous  sulphate 
is  introduced  into  the  liquid,  the  crystal  very  soon  assumes  a 


SULPHATES.  273 

brown  color  which  is  communicated  to  the  liquid.  In  this 
very  delicate  reaction  the  nitric  acid  is  reduced  by  the  ferrous 
sulphate  to  nitrogen  dioxide,  which  colors  the  excess  of  ferrous 
sulphate  brown  (page  154). 

The  solution  of  a  nitrate,  when  treated  with  sulphuric  acid, 
will  decolorize  solution  of  sulphate  of  indigo  when  the  liquid 
is  heated  to  boiling. 

SULPHATES. 

Composition. — Sulphuric  acid,  H2S04,  contains  two  atoms 
of  hydrogen  capable  of  being  replaced  by  a  metal.  When  both 
are  replaced  by  an  equivalent  quantity  of  metal,  a  neutral  sul- 
phate is  formed.  An  acid  sulphate  is  formed  when  a  single 
one  of  these  atoms  of  hydrogen  is  replaced  by  a  single  atom  of 
metal.  The  hydrogen  of  the  acid  is  removed  by  the  oxygen 
of  the  metallic  oxide  or  hydrate  which  more  or  less  completely 
saturates  the  sulphuric  acid.  Several  cases  may  be  presented. 

1.  K'OH       -f  H2S04  =        I'  j  SO4        +  H20 

Potassium  hydrate.  Potassium  acid  sulphate. 

2.  2K'OH     +     H2S04    =      K/2S04      +     2H20 

Potassium  sulphate. 

3.  Pb"0       -f     H2S04    =     Pb"S04     +     H20 

Plumbic  oxide.  Plumbic  sulphate. 

C  H2S04  C  SO4 

1  H2S04 


4.     (Al2)vi03     +    \  HSSO*  =  (AP/M  SO4  +  3H20 
(H2S04  (SO4 

Aluminium  oxide.  3  molecules.        Aluminium  sulphate. 

These  examples  show  that  all  of  the  sulphates  contain  the 
group  SO4,  which  in  sulphuric  acid  is  united  with  two  atoms 
of  hydrogen.  This  group  is  diatomic;  it  is  necessary,  then, 
that  in  the  sulphates  it  shall  be  united  with  a  quantity  of  metal 
equivalent  to  two  atoms  of  hydrogen. 

1.  In  the  acid  sulphates  it  is  united  with  an  atom  of  hydro- 

T>/  y 
gen  and  an  atom  of  a  monatomic  metal,  TT  >•  SO4. 

2.  It  is  united  with  two  atoms  of  a  monatomic  metal  in  the 
neutral  sulphates  E/2S04. 

3.  With  one  atom  of  a  diatomic  metal  in  the  neutral  sul- 
phates M"S04. 

These  cases  are  very  simple.     It  is  not  so,  however,  with 
M* 


274  ELEMENTS   OP   MODERN   CHEMISTRY. 

the  fourth,  in  which  we  consider  the  saturation  of  sulphuric 
acid  by  an  oxide  I1203,  such  as  ferric  oxide  or  aluminic  oxide. 
Each  of  the  three  atoms  of  oxygen  of  the  oxide  R203  removes 
H2  from  a  molecule  of  H2S04,  and  it  results  that  the  metal 
which  was  combined  with  30",  combines  with  3(S04)".  The 
two  atoms  of  metal  which  are  substituted  for  3H2  in  three  mol- 
ecules of  H2SO*  are  then  equivalent  to  6  atoms  of  hydrogen. 
They  are  hexatomic,  as  is  marked  by  the  index  vi. 

Properties. — The  sulphates  are  nearly  all  soluble  in  water. 
Those  of  barium,  strontium,  and  lead  are  insoluble.  The  sul- 
phates of  calcium  and  silver,  and  mercurous  sulphate  are  but 
slightly  soluble. 

The  alkaline  sulphates,  and  those  of  calcium,  barium,  stron- 
tium, magnesium,  and  lead,  are  undecomposable  by  heat.  The 
others  are  decomposed  at  a  high  temperature.  A  residue  of 
oxide  generally  remains,  while  sulphurous  oxide  and  oxygen 
are  disengaged.  The  sulphates  of  zinc  and  copper  are  thus 
decomposed  at  a  high  red  heat. 

CuSO4     =  SO2  +  0  +     CuO 

Cupric  sulphate.  Cupric  oxide. 

In  case  the  oxide  is  reducible  by  heat,  the  residue  consists 
of  metal. 

HgSO    =     Hg     +     SO2     +     O2 

Mercuric  sulphate.       Mercury. 

The  sulphates  R2(S04)3  are  decomposed  at  a  comparatively 
low  temperature,  disengaging  vapor  of  sulphur  trioxide  and 
leaving  a  residue  of  sesquioxide. 

Fe2(SO*)3     =     Fe203     -f     3S03 

Ferric  sulphate.  Ferric  oxide.      Sulphuric  oxide. 

The  sulphates  are  easily  reduced  by  bodies  avid  of  oxygen, 
such  as  charcoal. 

If  an  intimate  mixture  of  potassium  sulphate  with  an  excess 
of  charcoal  be  heated  to  bright  redness,  and  allowed  to  cool  out 
of  contact  with  the  air,  a  black  powder  is  obtained,  which  pro- 
duces a  shower  of  sparks  when  projected  into  the  air.  It  is 
the  pyrophorous  of  Gray-Lussac.  It  owes  its  spontaneous  in- 
flammability on  contact  with  the  air  to  finely-divided  potassium 
sulphide  which  it  contains,  and  which  attracts  oxygen  with  great 
avidity.  The  sulphide  is  formed  according  to  the  following 
reaction : 

K2S04    +     40    =    4CO     +'    K2S 

Potassium  sulphate.  Potassium  sulphide. 


CARBONATES.  2*75 

In  the  same  manner  barium  sulphate  and  calcium  sulphate 
are  converted  into  sulphides  by  the  action  of  charcoal  at  a  high 
temperature. 

The  other  sulphates  are  also  reduced  under  the  same  circum- 
stances, but  the  products  vary;  carbon  dioxide  or  carbon  mon- 
oxide and  sulphurous  oxide  are  disengaged,  and  the  residue 
consists  of  either  oxide  or  metal. 

Distinctive  Characters. — When  treated  by  sulphuric  acid, 
the  sulphates  do  not  evolve  any  gas.  They  do  not  deflagrate 
when  thrown  upon  burning  charcoal.  Their  solutions  give  a 
white  precipitate  of  barium  sulphate  with  barium  nitrate,  which 
is  insoluble  in  nitric  acid.  When  this  precipitate  is  washed, 
dried,  and  calcined  with  an  excess  of  charcoal,  it  leaves  a  resi- 
due of  barium  sulphide,  and  when  this  is  moistened  with  hy- 
drochloric acid,  it  evolves  hydrogen  sulphide,  which  is  easily 
recognized  by  its  odor. 

CARBONATES. 

Composition. — Carbonic  acid  is  dibasic,  like  sulphuric  acid. 
It  is  not  known  in  the  state  of  hydrate,  and  the  carbonates  are 
formed  by  the  direct  union  of  carbon  dioxide  with  the  metallic 
oxides  or  hydrates. 

When  freshly-burnt  lime  is  exposed  to  the  air,  it  attracts  at 
the  same  time  the  moisture  and  the  carbonic  acid  gas  of  the  air, 
and  is  converted  into  carbonate. 

CO2     -f     CaO     =     CaCO3 

Calcium  oxide.  Calcium  carbonate. 

The  carbonates  then  contain  the  group  CO3  combined  with 
a  metal.  In  carbonic  acid,  this  group  would  be  united  with  two 
atoms  of  hydrogen.  The  composition  of  the  more  simple  car- 
bonates is  expressed  by  the  following  formulae: 

H2C03  carbonic  acid  (unknown). 

R'  ) 

TT  [  CO3  acid  carbonates  (dicarbonates). 

R'2C03  neutral  carbonates. 
M"C03  neutral  carbonates. 

In  these  formulae,  R/  represents  a  monatomic  metal,  such  as 
potassium,  which  is  equivalent  to  one  atom  of  hydrogen.  M" 
represents  a  diatomic  metal,  such  as  calcium,  which  is  equiva- 
lent to  two  atoms  of  hydrogen. 

Properties. — Only  the  alkaline  carbonates  are  soluble  in  pure 


276  ELEMENTS    OF    MODERN    CHEMISTRY. 

water.  The  others  are  insoluble,  but  they  dissolve  in  water 
charged  with  carbonic  acid. 

The  soluble  carbonates  possess  an  alkaline  reaction.  It  is 
the  same  with  the  acid  carbonates  of  the  alkaline  metals,  which 
are  ordinarily  called  bicarbonates,  such  as  potassium  dicarbonate 
KHCO3. 

All  of  the  carbonates  except  the  alkaline  carbonates  are  de- 
composable by  heat.  In  this  decomposition  carbon  dioxide  is 
disengaged,  and  there  remains  a  residue  of  oxide,  or  of  metal 
in  case  the  oxide  be  reducible  by  heat.  Thus,  the  carbonates 
of  magnesium,  calcium,  zinc,  lead,  and  copper  leave  a  residue 
of  oxide  after  calcination ;  silver  carbonate  leaves  a  residue  of 
metal. 

Barium  carbonate  is  but  slowly  decomposed  at  a  white  heat ; 
its  decomposition  is  facilitated  by  heating  it  in  a  current  of 
steam. 

Bodies  avid  of  oxygen  act  upon  the  carbonates  as  upon  the 
oxides ;  the  metal  is  reduced  if  the  base  be  reducible.  Char- 
coal acts  in  this  manner  upon  the  carbonates. 

If  cupric  carbonate  be  heated  with  charcoal,  carbon  dioxide 
is  disengaged,  and  metallic  copper  remains. 

2CuC03     +  C  =  SCO2  -f  2Cu 

Cupric  carbonate.  Copper. 

In  this  experiment  carbon  dioxide  is  disengaged,  for  cupric 
oxide  is  easily  reducible  by  charcoal.  It  is  not  the  same  with 
potassium  oxide ;  hence  potassium  carbonate  is  only  reduced 
by  charcoal  at  a  very  high  temperature  with  disengagement 
of  carbon  monoxide. 

K2C03  +  20  =  3CO  -f  K2 

When  barium  carbonate  is  heated  with  charcoal,  carbon 
monoxide  is  disengaged  in  the  same  manner,  but  there  remains 
a  residue  of  barium  oxide,  for  the  latter  is  irreducible  by  char- 
coal. 

BaCO3  +  C  =  2CO  -f  BaO 

Phosphorus  decomposes  all  of  the  carbonates. 

A  small  piece  of  phosphorus  may  be  placed  at  the  bottom 
of  a  small  test-tube,  and  the  latter  then  nearly  filled  with  well- 
dried  sodium  carbonate.  The  part  of  the  tube  containing  the 
carbonate  being  heated  to  redness,  the  phosphorus  may  be 
heated  so  that  its  vapor  will  pass  over  the  incandescent  car- 


CLASSIFICATION   OF   THE   METALS.  277 

bonate.  The  latter  will  be  decomposed  with  the  formation  of 
sodium  phosphate  and  a  deposition  of  carbon.  After  cooling, 
the  contents  of  the  tube  will  be  black. 

The  experiment  may  be  repeated  upon  calcium  carbonate. 
The  phosphorus  is  placed  in  a  small  crucible,  which  is  then 
introduced  into  a  larger  one.  The  calcium  carbonate  (chalk) 
is  then  placed  upon  the  lid  of  the  smaller  crucible,  which  is 
pierced  with  holes.  The  arrangement  is  heated  upon  a  double 
grate,  so  that  when  the  chalk  has  been  brought  to  incandes- 
cence, the  vapor  of  phosphorus  may  be  caused  to  pass  through 
it  by  placing  some  hot  coals  upon  the  lower  grate.  The  chalk 
is  rapidly  decomposed,  carbon  monoxide  is  disengaged,  and  a 
mixture  of  calcium  phosphate  and  phosphide  is  formed.  This 
mixture  serves  for  the  preparation  of  hydrogen  phosphide. 

Distinctive  Characters.— When  treated  with  sulphuric  acid, 
the  carbonates  disengage  a  cblorless,  incombustible  gas,  which 
extinguishes  burning  bodies  and  produces  a  milkiness  when 
agitated  with  lime-water. 

CLASSIFICATION  OF  THE   METALS. 

In  the  preceding  pages  we  have  studied  the  composition  and 
the  general  properties  of  metallic  compounds.  This  study  has 
revealed  the  fact  that  the  metals  possess  very  different  aptitudes 
to  form  compounds,  and  various  capacities  of  combination,  which 
are  manifested  by  the  greater  or  less  number  of  other  atoms 
which  the  atoms  of  these  metals  can  attract.  In  this  respect, 
the  differences  existing  between  the  metals  are  analogous  to 
those  which  we  have  already  remarked  between  the  metalloids. 
On  comparing  the  metals  among  themselves,  some  are  discov- 
ered which  resemble  each  other  in  the  general  structure  of  the 
compounds  which  they  are  capable  of  forming,  and  such  can 
naturally  be  classed  in  the  same  group.  On  this  plan  the 
metals  are  divided  into  several  families  analogous  to  those  first 
proposed  by  Dumas  for  the  metalloids,  and  it  will  be  seen  that 
the  general  composition  of  the  metallic  compounds  furnishes 
the  elements  for  a  natural  classification  of  the  metals.  While 
this  principle  is  excellent,  its  application  is  attended  with  some 
difficulties  which  chemistry  has  not  yet  been  able  to  solve. 
Consequently,  this  chapter  must  be  limited  to  summary  indi- 
cations upon  the  subject. 

Some  of  the  metals  are  incapable  of  combining  with  more 
24 


278 


ELEMENTS    OF    MODERN    CHEMISTRY. 


than  a  single  atom  of  chlorine,  bromine,  or  iodine.  The  com- 
pounds thus  formed  correspond  in  their  atomic  constitution  to 
hydrochloric,  hydriodic,  and  hydrobromic  acids.  On  comparing 
potassium  chloride  or  silver  chloride  to  hydrochloric  acid,  it 
will  be  seen  that  an  atom  of  potassium  or  an  atom  of  silver 
occupies  in  them  the  place  occupied  by  the  hydrogen  of  the 
acid.  The  atoms  of  potassium  and  of  silver  are  therefore 
equivalent  to  the  atoms  of  hydrogen  as  far  as  their  capacity 
of  combination  is  concerned.  The  other  alkaline  metals,  such 
as  sodium  and  lithium,  are  similar  and  belong  to  the  same  group. 
Their  chlorides,  bromides,  and  iodides,  which  are  arranged  in  the 
following  table,  present  analogous  compositions  : 


MONATOMIC  METALS. 

MONATOMIC 
CHLORIDES. 

MONATOMIC 
BROMIDES. 

MONATOMIC 
IODIDES. 

H'Cl 

P,Br 

Ill 

Potassium  K'      
Sodium  Na'    

KC1 
NaCl 

KBr 
NaBr 

KI 

Nal 

LiCl 

LiBr 

Lil 

Silver  Ag'  

AgCl 

AgBr 

Agl 

These  metals  form  oxides  whose  atomic  constitutions  corre- 
spond to  that  of  water,  ea'ch  containing  two  atoms  of  metal  for 
one  of  oxygen.  Their  sulphides  correspond  to  hydrogen  sul- 
phide, containing  two  atoms  of  metal  for  one  of  sulphur.  "With 
the  oxides  and  sulphides  we  may  group  the  hydrates  and 
sulphydrates,  which  possess  analogous  atomic  constitutions. 

TYPE  H20.  TYPE  H2S. 

OXIDES.  HYDRATES.  MONOSIJLPHIDES.  SULPHYDRATES. 

K"0  KOH  K2S  KSH 

Na20  NaOH  Na2S  NaSII 

Ag«0  Ag'S 

The  same  analogy  is  continued  between  the  salts  of  these 
metals,  as  will  be  seen  from  the  nitrates  and  sulphates  which 
we  take  as  examples. 

NITRIC  ACID,  HNO3.  SULPHURIC  ACID,  IPSO4. 


NITRATES. 
KNOS 


SULPHATES. 


Na2SO* 


ACID  SULPHATES. 
KHSO* 
NaHSO* 


AgNO» 


CLASSIFICATION   OP   THE   METALS. 


279 


It  is  seen  that  in  all  of  these  compounds  the  metals  under 
consideration  replace  hydrogen  atom  for  atom ;  each  of  them 
possesses  the  same  capacity  of  combination  as  that  gas.  They 
are  said  to  be  monatomic. 

Certain  other  metals  manifest  a  double  capacity  of  combina- 
tion; one  atom  of  any  of  these  is  capable  of  replacing  two 
atoms  of  hydrogen,  consequently  it  can  combine  with  two 
atoms  of  chlorine,  bromine,  or  iodine,  or  with  one  atom  of 
oxygen  or  sulphur.  In  the  chlorides  of  these  metals,  the  two 
atomicities  of  the  metal  are  satisfied  by  the  two  atomicities  of 
two  atoms  of  chlorine.  In  their  oxides,  the  two  atomicities 
of  the  metal  are  satisfied  by  the  two  atomicities  or  bonds  of 
affinity  which  reside  in  one  atom  of  oxygen.  These  metals  are 
then  diatomic.  They  are  quite  numerous  and  can  be  divided 
into  several  groups,  one  of  the  most  natural  of  which  com- 
prises barium,  strontium,  calcium,  and  lead.  The  following 
table  shows  the  constitution  of  the  principal  compounds  of 
these  metals : 


DIATOMIC  METALS. 

CHLORIDES. 

OXIDES. 

NITRATES. 

SULPHATES. 

2HC1 

H20 

2HN03 

II2SO* 

Barium  Ba"     . 

Bad2 

BaO 

Ba(N03)2 

BaSO* 

Strontium  Sr"  . 

SrCl2 

SrO 

Sr(N03)2 

SrSO* 

Calcium  Ca"    . 

CaCl2 

CaO 

Ca(N03)2 

CaSO* 

Lead  Pb"    .     . 

PbCl2 

PbO 

Pb(N03)2 

PbSO* 

The  metals  of  this  group  combine  with  oxygen  in  two  pro- 
portions, forming  not  only  the  monoxides,  RO,  but  also  the 
dioxides,  RO2.  They  thus  form  two  oxides,  while  they  are 
capable  of  forming  but  one  chloride,  RCP.  Thus,  barium 
forms  a  monoxide,  BaO,  a  dioxide:  BaO2,  and  a  dichloride, 
BaCl2;  but  no  tetrachloride  of  barium  is  known,  and  it  is  not 
probable  that  barium  can  act  as  a  tetratomic  element.  How  is 
it,  then,  that  in  the  dioxide  this  metal  can  combine,  with  two 
atoms  of  oxygen,  while  it  cannot  combine  with  four  atoms  of 
chlorine,  which  are  equivalent  to  two  atoms  of  oxygen  ?  In 
other  words,  what  is  the  atomicity  of  barium  in  the  dioxide 
which  would  seem  to  correspond  to  a  tetrachloride  ?  It  is 


280  ELEMENTS   OP   MODERN   CHEMISTRY. 

undoubtedly  diatomic  in  the  dioxide  as  it  is  in  the  monoxide, 
and  the  constitution  of  barium  dioxide  is  analogous  to  that  of 
hydrogen  dioxide,  which  has  already  been  indicated.  The 
two  atoms  of  oxygen  mutually  satisfy  two  of  their  atomicities 
by  combining  together,  and  they  retain  two  which  are  neutral- 
ized in  combining  with  the  diatomic  atom  of  barium.  Thus, 
in  barium  monoxide  one  atom  of  oxygen  is  joined  to  one  atom 
of  barium  by  both  of  its  atomicities ;  in  the  dioxide  two  atoms 
of  oxygen  are  united  to  one  atom  of  barium,  each  by  one  atom- 
icity. If  we  represent  the  saturation  of  two  atomicities  by  a 
straight  line,  as  has  before  been  explained,  we  will  have  the 
following  formulae : 

Ba^O  Ba 

Barium  iuonoxLk\  /\ 

0-0 

Barium  dioxide. 

In  this  manner,  theory  enables  us  to  fix  the  relations  existing 
between  the  atoms  in  a  given  body. 

The  comparison  may  be  continued  between  the  other  diatomic 
metals.  Magnesium,  the  radical  of  magnesia,  somewhat  resem- 
bles calcium  in  its  relations,  and  forms,  as  it  were,  the  centre 
of  a  group  including  magnesium,  zinc,  cobalt,  and  nickel,  and 
which  is  called  the  magnesium  group.  Manganese  and  iron,  on 
one  hand,  and  copper,  on  the  other,  seem  to  join  this  group  by 
certain  of  their  characteristics.  In  their  most  stable  and  gen- 
erally their  most  important  compounds,  these  metals  act  as 
diatomic  elements.  All  form  the  dichlorides  RC12  and  the 
oxides  RO.  But  in  other  compounds,  manganese  and  iron 
seem  removed  from  the  metals  of  this  group,  and  resemble 
chromium  and  aluminium.  Copper,  which  resembles  magne- 
sium in  the  series  of  cupric  compounds,  approaches  mercury 
in  the  cuprous  series. 

Bismuth,  which  might  be  classed  with  antimony,  and  gold 
are  triatomic  in  their  most  important  combinations.  They 
form  the  chlorides  BiCl3  and  AuCP. 

A  certain  number  of  the  metals  may  be. grouped  together  as 
tetratomic,  since  they  manifest  four  atomicities  in  their  principal 
combinations.  They  are  tin,  titanium,  and  zirconium.  They 
form  the  chlorides  RC1*  and  the  oxides  RO2.  In  stannic  chlo- 
ride, SnCl4,  the  tin  is  saturated  with  chlorine,  of  which  it 
cannot  combine  with  more  than  four  atoms;  it  is  tetratomic 
in  this  saturated  compound.  But  it  may  combine  with  only 


CLASSIFICATION   OF   THE   METALS. 


281 


two  atoms  of  chlorine,  thus  forming  the  chloride  SnCl2, 
which  is  not  saturated,  for  it  can  still  fix  two  more  atoms 
of  chlorine.  Tin  only  manifests  two  atomicities  in  the 
dichloride. 

In  the  same  manner,  ferrous  chloride,  Fed2,  can  absorb 
chlorine,  becoming  ferric  chloride.  The  latter  contains  two 
atoms  of  iron  and  six  of  chlorine.  These  two  atoms  of  iron 
exist  in  all  the  ferric  compounds ;  together  they  manifest  six 
atomicities,  for  in  ferric  chloride  they  are  united  with  six  atoms 
of  chlorine.  They  constitute  a  hexatomic  couple. 


COMPOUNDS. 

CHLORIDES. 

OXIDES. 

SULPHATES. 

Fe2Cl6 

Fe203 

Fe2(S04)3 

Manganic   ...... 

Mn2Cl6 

Mn203 

Mn2(SO*)3 

Cr2Cl6 

Cr203 

Cr2(S04)3 

Aliiiniuic     .     .          ... 

A12C16 

A1203 

A12(S04)3 

The  following  table  gives  a  resume  of  the  constitution  of  the 
principal  metallic  combinations.  The  metals  there  chosen  as 
examples  have  different  atomicities.  The  hexatomic  couple, 
consisting  of  two  atoms  of  iron,  may  for  convenience  be  called 
ferricum. 


METALS. 

CHLORIDES. 

OXIDES. 

NITRATES. 

SULPHATES. 

Monatomic  metal—  Potassium  K'     . 

KC1 

K20 

KN03 

K2SO* 

Diatomic  metal  —  Barium  Ba"  .    .    . 

BaC12 

BaO 

Ba(N03)2 

BaSO* 

Triatomic  metal—  Bismuth  Bi'"   .    . 

BiC13 

Bi203 

Bi(N03)3 

Bi2(SO*)S 

Tetratomic  metal—  Tin  Sriiy     .    .    . 

SnCl* 

SnO2 

Hexatomic  group  —  Ferricum  (Fe2)vi 

Fe2C16 

Fe203 

Fe2(N03,6 

Fe2(SO*)3 

Such  are  the  principles  furnished  by  the  theory  of  atomicity 
for  a  rational  classification  of  the  metals. 


24* 


282  ELEMENTS   OF   MODERN   CHEMISTRY. 

POTASSIUM. 

K  =  39.1. 

Potassium  was  discovered  by  Sir  Humphry  Davy  in  1807. 
It  ordinarily  occurs  in  commerce  in  gray,  globular  masses, 
readily  yielding  to  the  pressure  of  the  nail.  It  has  a  dull, 
tarnished  appearance,  but  when  freshly  cut  it  exposes  a  brilliant 
surface.  It  is  the  metallic  radical  of  potash. 

If  a  fragment  of  this  metal  be  thrown  into  water,  it  at  once 
takes  fire  and  rushes  about  on  the  surface  of  the  liquid,  burn- 
ing with  a  violet  flame.  Finally,  it  disappears  with  a  little 
explosion. 

This  brilliant  phenomenon  is  due  to  the  energy  with  which 
potassium  decomposes  water. 

2H20  +  K2  =  2KOH  +  H2 

The  hydrogen  which  is  disengaged  is  inflamed  by  the  incan- 
descent metal.  The  potassium  hydrate  formed  ultimately  dis- 
solves in  the  water,  but  its  temperature  being  very  high  at  the 
moment  of  its  solution,  and  its  combination  with  the  water 
also  producing  heat,  there  results  a  sudden  formation  of  steam, 
which  gives  rise  to  the  little  explosion. 

Preparation  and  Properties. — Potassium  is  prepared  by 
decomposing  potassium  carbonate  by  carbon  at  a  high  tempera- 
ture. 

K2C03     +     20    =     SCO     +     K2 

Potassium  carbonate.  Carbon  monoxide. 

The  mixture  is  heated  to  whiteness  in  an  iron  retort  and  the 
vapors  are  passed  into  a  copper  receiver.  The  potassium  dis- 
tils and  condenses  in  globules  or  irregular  masses,  still  contain- 
ing charcoal  and  a  black  substance.  It  is  purified  by  redistilla- 
tion in  an  iron  retort,  and  is  condensed  in  a  copper  receiver 
filled  with  naphtha.  The  manufacture  of  potassium  is  a  dan- 
gerous operation.  It  is  accompanied  by  the  formation  of 
various  accessory  products,  among  which  is  a  black  substance 
which  sometimes  explodes  spontaneously  on  contact  with  the 
air. 

Potassium  melts  at  62.5°  (Bunsen).  It  boils  at  a  red  heat, 
and  its  vapor  is  green.  When  exposed  to  the  air,  it  rapidly 
absorbs  oxygen  and  at  the  same  time  decomposes  the  atmos- 
pheric moisture.  It  inflames  at  a  temperature  but  slightly 
elevated  and  becomes  converted  into  oxide. 


POTASSIUM    OXIDES. — POTASSIUM    HYDRATE. 


283 


POTASSIUM   OXIDES. 

Potassium  monoxide,  K20,  is  formed  when  thin  pieces  of 
the  metal  are  abandoned  to  the  action  of  dry  air,  or  when 
potassium  hydrate  is  heated  with  potassium. 

2KOH  +  K2  =  2K20  +  H2 

It  is  a  grayish- white  substance  which  unites  with  water  with 
extreme  violence,  forming  potassium  hydrate. 

K20  +  H20  =  2KOH 

A  tetroxide  of  potassium,  K204,  is  formed  when  potassium 
is  heated  in  an  excess  of  oxygen,  but  it  is  little  known. 

POTASSIUM   HYDRATE,  OR  CAUSTIC   POTASSA. 

KOH 

This  important  compound  is  prepared  by  boiling  1  part  of 
potassium  carbonate  with  12  parts  of  water,  and  gradually  add- 
ing milk  of  lime  to  the  boiling  liquid.  The  lime  combines 
with  the  carbonic  acid  forming  an  insoluble  carbonate,  while 
the  potassa  remains  in  solution. 

K2C03     -f     Ca(OH)2     =     CaCO3     +     2KOH 

Calcium  hydrate.       Calcium  carbonate. 

When  the  decomposition  is  finished  the  liquid  is  allowed  to 
settle,  and  the  clear  solution  decanted  and  rapidly  evaporated. 


FIG.  97. 


The  residue  is  melted  in  a  silver  dish  and  poured  out  upon  flat 
stone  slabs  or  cast  in  cylindrical  metallic  moulds  (Fig.  9*7). 

This  product  is  known  as  potash  by  lime.     It  is  impure. 
By  treating  it  with  alcohol,  which  dissolves  only  the  potassium 


284  ELEMENTS    OF    MODERN    CHEMISTRY. 

hydrate,  it  may  be  purified  from  lime,  and  the  salts  of  potas- 
sium it  may  contain,  and  especially  the  carbonate,  which  is 
formed  by  the  absorption  of  carbonic  acid  gas  from  the  air 
during  the  evaporation.  The  clear  alcoholic  solution  is  decanted, 
and  after  the  alcohol  has  been  expelled  by  distillation,  the  resi- 
due is  evaporated  to  dryness  and  fused  in  a  silver  dish.  It  is 
known  as  potash  by  alcohol. 

Recently-fused  potassium  hydrate  occurs  as  opaque,  white 
fragments  having  a  short  fibrous  fracture  and  a  density  of  2.1. 
It  melts  at  a  red  heat  and  volatilizes  at  whiteness ;  it  is  not 
decomposed  by  heat.  When  exposed  to  the  air,  it  absorbs  moist- 
ure and  carbonic  acid  gas,  and  deliquesces.  It  is  very  soluble 
in  water,  and  produces  heat  in  dissolving.  A  hydrate,  KOH 
-j-  2H20,  is  deposited  from  its  hot  and  very  concentrated  solu- 
tion in  acute  rhombohedra. 

Potassium  hydrate  is  decomposed  by  iron  at  a  white  heat : 
oxide  of  iron  is  formed,  and  hydrogen  and  potassium  vapor  are 
disengaged.  Gay-Lussac  and  Thenard  founded  a  process  for 
the  preparation  of  potassium  on  this  decomposition.  Until  then 
the  metal  had  only  been  obtained  in  small  quantities  by  Davy 
by  the  electrolysis  of  potassium  hydrate. 

Potassium  hydrate  is  very  caustic.  It  softens  and  destroys 
the  skin,  and  for  this  purpose  is  employed  in  surgery  as  a  caustic. 
It  manifests  the  properties  of  an  alkali  in  the  highest  degree ; 
these  are  its  solubility  in  water,  its  power  to  neutralize  the 
acids  and  decompose  a  great  number  of  metallic  solutions,  and 
its  corrosive  action  on  the  tissues.  This  alkalinity  may  be  shown 
by  the  energy  with  which  the  most  feeble  solutions  of  potassa 
restore  the  blue  color  to  reddened  litmus,  and  change  to  green 
the  tincture  of  violets. 

SULPHIDES   OF  POTASSIUM. 

Potassium  will  burn  in  vapor  of  sulphur.  It  unites  with 
the  latter  body  in  five  different  proportions,  forming  the  sul- 
phides K2S,  K'S2,  K2S3,  K2S4,  and  K2S5. 

Potassium  monosulphide  is  formed  when  potassium  sulphate 
is  heated  to  redness  in  a  current  of  hydrogen,  or  in  a  brasqued1 
and  covered  crucible  with  charcoal. 

1  A  brasqued  crucible  is  a  clay  crucible  into  which  powdered  charcoal 
moistened  with  gum-water  has  been  strongly  pressed,  and  afterwards  cal- 
cined. The  substance  to  be  reduced  is  placed  in  a  cavity  hollowed  out  in 
the  charcoal. 


POTASSIUM   CHLORIDE. — POTASSIUM    IODIDE.  285 

K2S04    +    4C    =    4CO     +     K2S 

Potassium  sulphate.  Potassium  monosulphide. 

A  reddish,  deliquescent,  and  caustic  mass  is  thus  obtained. 
When  a  mixture  of  sulphur  and  potassium  carbonate  is  fused, 
carbon  dioxide  is  disengaged,  and  a  brown  mass  is  obtained  on 
cooling,  which  is  known  as  liver  of  sulphur.  It  is  a  mixture 
of  potassium  polysulphide  with  undecomposed  carbonate  and 
potassium  sulphate  or  hyposulphite,  according  to  the  tempera- 
ture and  the  proportions  of  sulphur  which  have  been  employed. 
With  an  excess  of  sulphur,  potassium  pentasulphide  is  obtained. 
Liver  of  sulphur  dissolves  in  water  with  a  brown-yellow  color. 

Potassium  pentasulphide  and  hyposulphite  are  also  formed 
when  potassium  hydrate  is  boiled  with  an  excess  of  flowers  of 
sulphur.  The  filtered  solution  is  brown.  When  treated  with 
hydrochloric  acid,  it  evolves  hydrogen  sulphide,  and  finely- 
divided,  yellowish,  pulverulent  sulphur  is  deposited. 
K2S5  +  2HC1  =  2KC1  -h  H2S  +  S4 

POTASSIUM  CHLORIDE. 

KC1 

This  salt  is  found  crystallized  in  cubes  in  the  neighborhood 
of  certain  fissures  of  Vesuvius,  and  in  thin  layers  in  the  saline 
deposits  at  Stassfurth,  Prussia,  and  in  other  localities.  At 
Stassfurth  there  is  found  a  double  chloride  of  potassium  and 
magnesium,  KCl,MgCl2  -f  6H20.  When  this  double  salt  is 
dissolved  in  hot  water,  the  greater  part  of  the  potassium 
chloride  is  deposited  on  cooling  while  the  magnesium  chloride 
remains  in  solution. 

Potassium  chloride  crystallizes  in  cubes,  but  it  sometimes 
separates  in  octahedra  from  solutions  containing  free  potassa. 
It  is  unaltered  by  the  air.  Its  taste  is  analogous  to  that  of 
sodium  chloride ;  it  is  more  soluble  in  water  than  the  latter, 
and  produces  a  greater  depression  of  temperature  in  dissolving. 
.  1  part  of  chloride  of  potassium  dissolves  in  3  parts  of  water 
at  17.5°.  100  parts  of  water  at  0°  dissolve  29.23  parts  of 
potassium  chloride  and  0.2738  additional  for  each  degree  of 
temperature. 

POTASSIUM  IODIDE. 
KI 

This  compound  is  quite  important  on  account  of  its  use  in 
medicine.  It  is  obtained  by  adding  powdered  iodine  to  solution 


236  ELEMENTS   OP   MODERN   CHEMISTRY. 

of  potassium  hydrate  until  the  latter  is  completely  neutralized. 
Potassium  iodide  and  iodate  are  formed,  the  latter  being  pre- 
cipitated. The  whole  is  evaporated  to  dryness,  and  the  residue 
heated  to  redness,  by  which  the  iodate  is  converted  into  iodide. 
The  mass  is  redissolved  in  boiling  water  and  the  solution  con- 
centrated ;  fine  cubical  crystals  of  potassium  iodide  are  obtained 
on  cooling. 

These  crystals  are  opaque  and  anhydrous.  They  melt  at  a 
red  heat  without  decomposition  ;  their  taste  is  salty  and  some- 
what bitter.  100  parts  of  water  at  18°  dissolve  143  parts  of 
potassium  iodide. 

A  solution  of  potassium  iodide  dissolves  iodine  abundantly, 
assuming  a  dark-brown  color. 

If  nitric  acid  be  added  to  a  solution  of  potassium  iodide, 
iodine  is  at  once  deposited  and  red  vapors  are  disengaged  if 
the  solution  be  concentrated  (page  131). 

This  decomposition  of  potassium  iodide  takes  place  even  in 
very  dilute  solutions.  It  may  serve  for  the  detection  of  the 
smallest  trace  of  this  salt  if  a  solution  of  starch  be  previously 
added  to  the  liquid  ;  in  this  case  a  blue  color  will  be  produced. 

Potassium  bromide  is  prepared  by  a  process  similar  to  that 
which  yields  potassium  iodide.  It  crystallizes  in  cubes  which 
are  soluble  in  about  1.5  parts  of  cold  water. 

POTASSIUM   NITRATE. 


This  important  salt,  long  known  as  nitre  and  saltpetre,  im- 
pregnates the  soil  and  sometimes  effloresces  upon  its  surface  in 
certain  regions  of  India,  Egypt,  Persia,  Hungary,  and  Spain. 
In  the  United  States,  it  is  found  in  many  localities,  generally 
in  caverns  in  limestone  rock,  called  saltpetre  caves.  It  is 
obtained  by  lixiviating  the  earthy  matters  containing  it  and 
evaporating  the  solution. 

It  is  less  abundant  in  northern  climates.  It  is  formed 
wherever  nitrogenized  organic  substances  decompose  in  pres- 
ence of  potassa.  Thus,  it  exists  in  small  quantities  in  the  soil 
of  cellars,  in  moist  walls,  and  in  the  debris  of  demolitions. 
In  these  cases  it  is  mixed  with  a  certain  quantity  of  sodium 
nitrate  and  a  large  excess  of  calcium  and  magnesium  nitrates. 
Formerly  such  materials  were  lixiviated  to  obtain  the  nitrates, 
all  of  which  were  then  converted  into  potassium  nitrate.  Nitre 
is  also  manufactured  artificially  by  exposing  to  the  air  mixtures 


POTASSIUM    NITRATE.  287 

of  animal  matters  with  wood-ashes  and  lime  which  are  fre- 
quently moistened  with  stale  urine  or  stable-drainings.  How- 
ever, a  great  part  of  the  potassium  nitrate  employed  in  the 
arts  is  now  obtained  from  the  natural  sodium  nitrate  of  Peru. 
Two  processes  are  employed. 

One  consists  in  adding  the  sodium  nitrate  to  a  concentrated 
boiling  solution  of  potassium  carbonate :  sodium  carbonate 
being  less  soluble  than  the  latter,  is  precipitated  and  continues 
to  deposit  during  the  concentration ;  it  is  removed,  and  the 
potassium  nitrate,  which  is  very  soluble  in  hot  water,  crystal- 
lizes out  on  cooling. 

The  second  process  consists  in  decomposing  the  sodium  nitrate 
with  potassium  chloride.  The  saturated  and  boiling  mixture 
of  the  two  solutions  deposits  sodium  chloride,  which  is  sepa- 
rated, and  the  potassium  nitrate  crystallizes  on  cooling. 

Properties. — This  salt  crystallizes  from  its  aqueous  solution 
in  long,  six-sided  prisms,  terminated  by  six-sided  pyramids.  Gen- 
erally these  crystals  are  grooved  or  striated.  They  belong  to  the 
right  rhombic  system.  Their  taste  is  cooling  and  slightly  bitter. 

Potassium  nitrate  melts  at  about  350°  ;  at  a  higher  tem- 
perature it  disengages  oxygen  and  is  converted  into  potassium 
nitrite,  KNO2,  which  is  in  its  turn  decomposed  at  a  red  heat, 
leaving  a  mixture  of  oxide  and  peroxide  of  potassium. 

Potassium  nitrate  is  very  soluble  in  hot  water :  100  parts  of 
water  at  0°  dissolve  only  13.32  parts  of  the  salt,  but  at  18°  they 
dissolve  29  parts ;  at  97°,  236  parts ;  and  at  100°,  246  parts. 

The  facility  with  which  potassium  nitrate  parts  with  its  oxy- 
gen, of  which  it  contains  nearly  half  its  weight,  renders  it  an 
energetic  oxidizer  of  many  bodies. 

If  a  small  quantity  of  pulverized  saltpetre  be  thrown  upon 
glowing  coals,  the  salt  melts  and  decomposes,  increasing  the 
combustion  at  the  point  of  contact  with  the  fuel :  it  is  said  to 
deflagrate  upon  hot  coals.  The  nitrate  becomes  converted  into 
carbonate. 

Gunpowder  is  an  intimate  mixture  of  saltpetre,  charcoal, 
and  sulphur.  As  is  well  known,  the  combustion  of  this  sub- 
stance is  instantaneous,  and  gives  rise  to  the  sudden  formation 
of  gaseous  products.  The  decomposition  may  be  expressed 
generally  by  stating  that  the  charcoal  combines  with  the  oxy- 
gen of  the  nitre  to  form  carbon  dioxide  and  carbon  monoxide ; 
the  nitrogen  is  liberated,  and  the  sulphur  combines  with  the 
potassium  forming  potassium  sulphide.  As  the  mixture  con- 


288  ELEMENTS   OF    MODERN   CHEMISTRY. 

tains  all  of  the  oxygen  necessary  for  its  own  combustion,  the 
latter  can  be  effected  in  a  limited  and  closed  space.  It  can 
readily  be  understood  that  the  explosive  energy  of  the  powder 
is  due  to  a  sudden  evolution  of  gas  occupying  many  times  the 
volume  of  the  powder,  and  of  which  the  volume  is  still  further 
augmented  by  the  high  temperature. 

POTASSIUM   SULPHATE. 


This  salt  is  obtained  as  a  by-product  in  various  industrial 
operations.  It  deposits  from  the  mother-liquors  of  the  soda 
from  sea-weed  when  these  are  exposed  to  low  temperatures.  It 
may  be  made  by  saturating  with  potassium  carbonate  the  potas- 
sium acid  sulphate  which  is  formed  in  the  preparation  of  nitric 
acid  by  the  decomposition  of  potassium  nitrate  with  sulphuric 
acid,  a  process  which  is  now  but  little  employed. 

It  crystallizes  in  four-sided  prisms  or  in  double,  six-sided 
pyramids  belonging  to  the  orthorhombic  system.  These  crys- 
tals are  hard,  anhydrous,  unaltered  by  the  air,  and  melt  at  a 
red  heat  without  decomposition.  They  are  but  slightly  soluble 
in  water  and  insoluble  in  absolute  alcohol.  100  parts  of  water 
at  0°  dissolve  8.36  parts,  and  0.1741  part  for  each  additional 
degree  of  heat. 

POTASSIUM  ACID  SULPHATE. 


This  salt  may  be  obtained  by  fusing  13  parts  of  the  neutral 
sulphate  with  8  parts  of  concentrated  sulphuric  acid.  The 
saline  mass  is  dissolved  in  boiling  water,  and  the  solution  when 
properly  concentrated  deposits  rhombic  octahedra  or  tabular 
crystals  belonging  to  the  orthorhombic  system. 

Potassium  acid  sulphate  is  much  more  soluble  in  water  than 
the  neutral  salt  ;  its  solution  is  acid.  When  strongly  heated, 
it  first  gives  up  water  and  then  sulphuric  oxide,  leaving  a  resi- 
due of  neutral  sulphate. 

POTASSIUM   CHLORATE. 

KC1Q3 

This  salt  is  formed,  together  with  potassium  chloride,  by  the 
action  of  chlorine  upon  a  concentrated  solution  of  potassium 
hydrate  or  carbonate  : 

6C1  +  6KOH  ==  KC103  +  5KC1  +  3H20 


POTASSIUM   PERCHLORATE.  289 

It  is  less  soluble  than  the  chloride,  and  is  consequently  de- 
posited in  great  part  as  the  solution  becomes  saturated  with 
chlorine.  It  is  purified  by  several  recrystallizations. 

In  the  arts,  it  is  obtained  by  the  action  of  chlorine  upon  a 
mixture  of  lime,  potassium  chloride,  and  water,  heated  in  closed 
vessels.  Chlorate  and  chloride  of  calcium  are  formed,  and  in 
presence  of  the  potassium  chloride,  a  double  decomposition  takes 
place,  potassium  chlorate  and  calcium  chloride,  which  is  very 
soluble,  being  formed.  The  liquid  is  filtered  hot,  and  the  potas- 
sium chlorate  crystallizes  out  on  cooling. 

KC1     -f     3CaO     +     3CP     =     KC103     +     3CaCl2 

Calcium  oxide.  Calcium  chloride. 

Potassium  chlorate  crystallizes  in  colorless,  rhomboidal  tables. 
When  very  thin  they  present  an  iridescent  reflection.  It  melts 
at  400°,  and  at  a  higher  temperature  is  decomposed  into  oxygen 
and  chloride  and  perchlorate  of  potassium,  the  latter  of  which 
is  also  decomposed  when  the  temperature  is  raised  still  further. 

2KC103  =  KC1  -f  KC10*  -f  O2 
KC104  =  KC1  +  O4 

Potassium  chlorate  deflagrates  when  thrown  upon  hot  coals  5 
when  mixed  with  sulphur,  it  explodes  by  friction  or  percussion  ; 
the  detonation  becomes  dangerous  if  the  sulphur  be  replaced 
by  phosphorus. 

It  is  not  very  soluble  in  cold  water.  100  parts  of  water  at 
0°  dissolve  3.3  parts,  and  at  24°,  8.44  parts.  It  is  much  more 
soluble  in  boiling  water. 

POTASSIUM  PERCHLORATE. 

KC10* 

This  salt  is  formed  by  the  action  of  either  heat  or  sulphuric 
acid  upon  potassium  chlorate  (page  124).  It  is  but  slightly 
soluble  in  water,  requiring  65  parts  at  15°  for  its  solution.  It 
crystallizes  in  anhydrous  and  transparent  right  rhombic  prisms. 
Above  400°  it  decomposes  into  potassium  chloride  and  oxygen. 

POTASSIUM   CARBONATES. 

Potassium  Neutral  Carbonate,  K2C03. — This  carbonate 
is  found  in  commerce  under  the  simple  name  potash,  and  is 
known  according  to  its  source  as  Russian  or  American  potash. 
N  25 


290  ELEMENTS    OF    MODERN    CHEMISTRY. 

It  is  obtained  by  lixiviating  wood  ashes ;  that  is,  exhausting 
them  with  water,  evaporating  the  solution  to  dryness,  and  cal- 
cining the  residue  in  the  air.  The  potash  thus  obtained  is 
impure  carbonate  mixed  with  other  salts  of  potassium,  princi- 
pally the  chloride  and  sulphate,  and  small  quantities  of  silicate. 
It  contains  from  60  to  80  per  cent,  of  carbonate. 

Potassium  carbonate  is  now  manufactured  from  the  native 
chloride,  Stassfurth  salt,  by  a  process  similar  to  that  which  will 
be  described  for  the  manufacture  of  sodium  carbonate  from 
common  salt. 

Pure  potassium  carbonate  may  be  prepared  by  calcining  potas- 
sium acid  tartrate,  or  cream  of  tartar,  at  a  red  heat.  A  black 
mass  is  thus  obtained  from  which  water  dissolves  pure  potas- 
sium carbonate,  and  the  solution  is  evaporated  to  dryness. 

Neutral  potassium  carbonate  is  very  soluble  in  water,  and 
absorbs  moisture  from  the  air.  1  part  of  the  anhydrous  salt 
dissolves  in  1.05  parts  of  water  at  3°,  and  in  0.49  parts  at  70° 
(Osann).  The  solution  has  a  decided  alkaline  reaction.  A 
very  concentrated  hot  solution  deposits  rhombic  octahedra 
containing  K2C03  -f-  2H20  on  cooling. 

Potassium  Acid  Carbonate,  KHCO3. — When  a  current  of 
carbonic  acid  gas  is  passed  into  a  concentrated  solution  of  potas- 
sium neutral  carbonate,  the  gas  is  absorbed,  and  crystals  of 
potassium  acid  carbonate,  ordinarily  known  as  bicarbonate  of 
potassa,  are  formed. 

It  represents  carbonic  acid  in  which  a  single  atom  of  hydro- 
gen is  replaced  by  an  atom  of  potassium. 

CO2  +  H20    =  HPCO*  carbonic  acid  (hypothetical). 
CO2  +  KHO  =  JJ  |  CO3  potassium  acid  carbonate. 
CO2  +  K20    =  K2C03  potassium  carbonate. 

Potassium  acid  carbonate  readily  crystallizes  in  oblique  rhom- 
bic prisms.  It  is  much  less  soluble  in  water  than  the  neutral 
carbonate,  and  its  solution  disengages  carbonic  acid  gas  on 
boiling.  Its  reaction  is  alkaline. 

Characters  of  Potassium  Salts. — The  salts  of  potassium 
communicate  a  violet  tint  to  flame.  Their  solutions  are  not 
precipitated  either  by  hydrogen  sulphide,  ammonium  sulphide, 
or  sodium  carbonate. 

Perchloric  acid  occasions  a  white  precipitate  of  potassium 
perchlorate. 


SODIUM. 


291 


Platinum  tetrachloride  produces  a  yellow,  crystalline  precipi- 
tate of  platinum  and  potassium  double  chloride,  2KCl.PtCl4. 

Hydrofluosilicic  acid  forms  a  white,  gelatinous  precipitate 
consisting  of  potassium  fluosilicate. 


SODIUM. 

Na  ==  23 

Sodium  was  discovered  by  Sir  Humphry  Davy  in  1807.  It 
is  made  by  decomposing  sodium  carbonate  with  charcoal,  a 
certain  proportion  of  chalk  being  added  to  render  the  mixture 
infusible.  The  operation  is  conducted  in  large  cast-iron  cylin- 


FIG.  98. 


ders  covered  with  a  refractory  luting  to  enable  them  to  resist 
the  high  temperature  required  to  effect  the  decomposition. 
The  vapor  passes  into  a  flattened  receiver  in  which  the  sodium 
condenses,  and  from  which  it  runs  into  appropriate  vessels 
(Fig.  98). 


292  ELEMENTS   OF   MODERN   CHEMISTRY. 

This  metal  is  soft  at  the  ordinary  temperature.  It  has  a 
silvery  lustre,  melts  at  90.6°,  and  distils  at  a  red  heat.  It  is 
not  as  avid  of  oxygen  as  potassium ;  it  can  be  melted  in  the 
air  without  taking  fire.  When  thrown  upon  water,  it  melts 
and  runs  around  on  the  surface,  producing  a  hissing  noise. 
The  water  is  decomposed  with  disengagement  of  hydrogen  and 
the  formation  of  sodium  hydrate.  The  reaction  is  analogous 
to  that  of  potassium  upon  water,  but  is  less  energetic;  fre- 
quently, however,  it  terminates  by  an  explosion. 

If  sodium  be  thrown  upon  hot  water,  or  water  which  has 
been  thickened  with  gum  or  starch,  so  that  the  consistence 
of  the  liquid  may  prevent  the  globule  from  moving  rapidly, 
the  latter  becomes  sufficiently  heated  to  ignite  the  hydrogen 
evolved,  which  then  burns  with  a  yellow  flame. 


The  compounds  of  sodium  are  widely  diffused  in  nature,  and 
generally  present  great  analogies  with  the  corresponding  potas- 
sium compounds. 

OXIDES   AND   HYDRATE   OF   SODIUM. 

Two  oxides  of  sodium  are  known,  a  monoxide,  Na20,  and  a 
dioxide,  Na202. 

Sodium,  hydrate,  NaOH,  is  frequently  employed  in  the  lab- 
oratory and  in  the  arts  under  the  name  caustic  soda.  It  is 
prepared  by  decomposing  a  rather  dilute,  boiling  solution  of  so- 
dium carbonate  by  milk  of  lime,  in  the  manner  described  for 
the  preparation  of  potassium  hydrate  (page  283).  It  occurs 
as  a  white  solid,  which  attracts  moisture  and  carbonic  acid 
from  the  air,  and  finally  becomes  transformed  into  a  dry  mass 
of  carbonate.  Sodium  hydrate  is  freely  soluble  in  water,  and  is 
very  caustic.  It  is  known  in  commerce  as  concentrated  lye. 

SODIUM   SULPHIDE   AND  SULPHYDRATE. 

Sodium  sulphide,  Na2S,  is  prepared  by  the  following  pro- 
cess: A  concentrated  solution  of  sodium  hydrate  is  divided 
into  two  equal  parts ;  one  part  is  then  saturated  with  hydrogen 
sulphide,  sodium  sulphydrate  being  formed. 

NaOH     +  H2S  =       NaSH       +  H20 

Sodium  hydrate.  Sodium  sulphydrate. 


SODIUM    CHLORIDE.  293 

To  this  sulphydrate  the  other  portion  of  sodium  hydrate  is 
added,  and  the  solution  is  concentrated  out  of  contact  with  the 
air.  Hydrated  crystals  of  sodium  sulphide  are  deposited. 

NaSH  +  NaOH  =  H20  +  Na2S 

These  crystals  are  rectangular  prisms  terminated  by  four- 
faced  points.  When  pure,  they  are  colorless;  they  are  very 
soluble  in  water. 

SODIUM   CHLORIDE. 

NaCl 

This  body  is  common  salt,  or  sea-salt.  It  is  widely  diffused 
in  nature.  It  is  found  in  the  solid  state,  as  rock-salt,  in  large 
deposits  in  many  countries. 

Sea-water  contains  a  large  proportion  of  sodium  chloride, 
and  this  salt  also  exists  in  a  number  of  mineral  waters,  of 
which  it  forms  the  most  abundant  constituent. 

In  France,  the  greater  portion  of  the  salt  delivered  to  com- 
merce is  obtained  by  the  evaporation  of  sea-water  in  the  salt- 
marshes  near  the  ocean,  and  the  salt-basins  along  the  Mediter- 
ranean. These  are  extensive  basins  into  which  the  water  is 
led  from  the  sea,  and  where  it  forms  a  shallow  layer,  which  is 
continually  swept  by  the  summer  winds.  It  thus  becomes  con- 
centrated, and  the  concentration  is  favored  by  the  water  being 
continually  kept  in  motion  from  one  basin  to  another,  until  it 
arrives  in  the  areas  where  the  salt  is  deposited.  The  mother- 
liquors,  from  which  the  sodium  chloride  is  separated,  and  which 
are  still  saturated  with  that  salt,  contain,  in  addition,  magne- 
sium sulphate  and  salts  of  potassium.  By  cooling  them  to  a 
low  temperature  sodium  sulphate  is  obtained,  being  formed  by 
a  double  decomposition  between  the  sodium  chloride  and  the 
magnesium  sulphate.  The  new  mother-liquor  then  deposits, 
first,  potassium  and  magnesium  double  sulphate,  and  after- 
wards, magnesium  and  potassium  double  chloride  (Balard).  It 
was  in  the  latter  of  these  liquors  that  Balard  discovered  bro- 
mine in  1826. 

Sodium  chloride  is  also  obtained  by  the  evaporation  of  the 
waters  of  salt  springs.  The  operation  is  conducted  in  large 
sheet-iron  boilers ;  the  salt  crystallizes  from  the  hot  liquid,  and 
a  double  sulphate  of  calcium  and  sodium,  which  is  but  slightly 
soluble,  deposits  in  the  basins  in  the  course  of  time. 

25* 


294  ELEMENTS    OF    MODERN    CHEMISTRY. 

Sodium   chloride  crystallizes  from  its  aqueous  solution  in 
cubes.     The  crystals  are  generally  small,  and  a  great  number 
of  them  frequently  become  agglomer- 
ated in  symmetrical  hopper-like  masses 
(Fig.  99).     These  crystals  are  anhy- 
drous, but  contain  a  small  quantity  of 
interposed  water  ;   when  heated  they 
decrepitate,  because  this  water  is  vola- 
FIG.  99.  tilized  and  suddenly  separates  the  crys- 

tals.    Rock-salt  is  sometimes  found  in 

transparent  cubes,  sometimes  in  octahedra  and  intermediate 
forms.  Sodium  chloride  fuses  at  a  red  heat  and  solidifies  to  a 
crystalline  mass  on  cooling.  It  volatilizes  at  a  white  heat.  It 
is  very  soluble  in  water,  and  its  solubility  does  not  increase  with 
the  temperature.  According  to  Gay-Lussac, 

1  part  of  common  salt  dissolves  in  2.78  parts  of  water  at     14° 
"  "  "  2.7         "  "  60° 

"  "  "  2.48       "  "  109.7° 

The  saturated  solution  boils  at  109.7° ;  its  density  at  8°  is 
1;205.     Sodium  chloride  is  insoluble  in  absolute  alcohol. 


SODIUM  SULPHATE. 


This  salt  is  obtained  in  the  arts  by  decomposing  common  salt 
with  sulphuric  acid  (page  117). 

This  operation,  which  constitutes  the  first  step  in  the  manu- 
facture of  sodium  carbonate,  is  conducted  in  a  reverberatory 
furnace,  connected  with  a  suitable  apparatus  for  the  condensa- 
tion of  the  hydrochloric  acid  which  is  disengaged.  Sodium 
acid  sulphate  is  first  formed,  and  at  a  higher  temperature  this 
reacts  upon  another  molecule  of  sodium  chloride. 


+     NaCl    =     Na2SO     +     HC1 

Sodium  acid  sulphate.  Sodium  sulphate. 

Sodium  sulphate  is  now  extensively  produced  by  subjecting 
the  mother-liquors  from  the  manufacture  of  salt  from  sea-water 
to  intense  cold. 

It  crystallizes  from  water  in  four-sided,  oblique  rhombic 
prisms,  containing  10  molecules  of  water  of  crystallization; 


SODIUM    CARBONATE.  295 

these  crystals  effloresce  in  the  air.  They  possess  a  bitter,  salty, 
and  disagreeable  taste.  They  are  very  soluble  in  water,  and 
the  temperature  of  their  maximum  solubility  is  33°.  Accord- 
ing to  Gay-Lussac, 

100  parts  of  water  at    0°  dissolve     12  parts  of  sodium  sulphate. 
u  «  is0        "          48  "  " 

«  «  25°        "         100  "  " 

«  •<  33°        "         332.6        "  " 

«  «  5QQ        «        263  "  " 

When  the  solution  saturated  at  33°  is  heated,  it  deposits  an- 
hydrous sodium  sulphate  in  orthorhombic  octahedra,  analogous 
to  the  anhydrous  sodium  sulphate  found  in  nature  (thenardite). 

Sodium  Acid  Sulphate,  ^  I  SO4.— This  salt  may  be  ob- 
tained by  dissolving  in  water  the  requisite  proportions  of  so- 
dium neutral  sulphate  and  sulphuric  acid.  On  cooling  the 
saturated  solution,  oblique  rhombic  prisms  are  obtained,  which, 
according  to  Mitscherlich,  contain  two  molecules  of  water  of 
crystallization.  These  crystals  are  very  soluble  in  water,  and 
have  an  acid  taste.  Alcohol  decomposes  them  into  sulphuric 
acid,  which  dissolves,  and  neutral  sulphate,  which  precipitates. 


SODIUM    CARBONATE. 

Na2CO3 

This  important  salt,  known  also  as  soda  and  sal-soda,  is 
manufactured  on  an  immense  scale  in  the  arts.  It  is  used  in 
the  manufacture  of  soap  and  glass,  for  washing,  and  many  other 
purposes.  It  was  formerly  obtained  from  the  ashes  of  fuci, 
algae,  and  other  sea-plants  which  furnished  Alicant  soda.  It 
is  now  most  generally  prepared  from  sodium  chloride,  and  the 
process,  which  is  due  to  Le  Blanc,  consists  of  three  distinct 
operations:  1st,  the  transformation  of  the  sodium  chloride 
into  sulphate  by  sulphuric  acid ;  2d,  the  conversion  of  the  sul- 
phate into  carbonate  by  calcination  with  a  mixture  of  chalk 
and  coal ;  3d,  lixiviation  of  the  calcined  mass  and  evaporation 
of  the  solution.  Only  the  latter  two  operations  need  be  de- 
scribed here :  they  are  conducted  in  reverberatory  furnaces, 
of  which  the  doubly-arched  roofs  are  licked  by  the  flame  of 
the  combustible  (Fig.  100). 


296  ELEMENTS   OF   MODERN   CHEMISTRY. 

A  mixture  of  1000  parts  of  sodium  sulphate,  1040  parts  of 
chalk,  and  580  parts  of  coal,  is  first  introduced  into  compart- 
ment B  of  the  furnace,  where  it  is  dried.  It  is  then  transferred 
to  compartment  A,  where  the  temperature  is  very  elevated, 
and  where  the  sodium  sulphate  is  reduced  to  sulphide  by  the 


FIG.  100. 

coal.     The  sodium  sulphide  and  chalk  react  upon  each  other, 
forming  sodium  carbonate  and  calcium  sulphide  (Kolb). 

The  results  of  the  reaction  may  be  expressed  by  the  follow- 
ing equation : 

Na2S04  +  CaCO3  +  O  =  Na2C03  -f  CaS  +  4CO. 

There  are,  however,  certain  secondary  reactions  which  take 
place  at  the  same  time ;  thus,  a  certain  quantity  of  sodium 
oxide  is  formed  by  the  action  of  the  coal  upon  the  carbonate. 

Na2C03  +  C  =  2CO  +  Na20 

When  the  incandescent  mass  has  become  pasty,  it  is  removed 
from  the  furnace,  reduced  to  powder,  and  thoroughly  lixiviated. 
The  water  dissolves  the  sodium  carbonate,  and  leaves  the  in- 
soluble calcium  sulphide,  which  remains  mixed  with  the  lime 
produced  by  the  decomposition  of  the  excess  of  chalk  employed 
(Gossage,  Scheurer-Kestner).  The  solutions  are  concentrated 
in  the  boiler  D,  heated  by  the  waste  heat  from  the  soda  fur- 
nace. Finally,  they  are  drawn  off  into  the  compartment  C, 
where  they  are  evaporated  to  dryness.  The  sal-soda  of  com- 
merce is  thus  obtained.  When  the  properly-concentrated  solu- 
tion is  allowed  to  cool,  the  crystallized  soda  of  commerce  is 
deposited. 

Another  process,  proposed  by  Schloesing  and  Holland,  is  also 
used  for  the  fabrication  of  sodium  carbonate. 


SODIUM    CARBONATE.  29*7 

It  depends  upon  the  double  decomposition  which  takes  place 
between  ammonium  acid  carbonate  and  sodium  chloride  in 
concentrated  aqueous  solution. 

NaCl  -f  (NH4)HC03  =  NIPC1  +  NaHCO3 

The  sodium  acid  carbonate,  which  is  but  slightly  soluble,  is 
precipitated ;  it  is  collected  and  converted  into  the  neutral  car- 
bonate by  the  action  of  heat. 

2NaHC03  =  Na2C03  +  CO2  +  H20 

It  thus  loses  half  of  its  carbonic  acid,  which  is  utilized  for 
the  preparation  of  a  new  quantity  of  ammonium  acid  carbonate. 
The  other  portion  of  the  carbonic  acid  necessary  for  this  oper- 
ation is  produced  by  the  calcination  of  lime-stone  (calcium  car- 
bonate), which  at  the  same  time  yields  the  lime  necessary  for 
the  liberation  of  the  ammonia  contained  in  the  mother-liquor 
in  the  form  of  ammonium  chloride. 

A  considerable  quantity  of  sodium  chloride  is  also  manufac- 
tured from  cryolite,  which  is  a  double  fluoride  of  sodium  and 
aluminium,  and  of  which  large  deposits  exist  in  Greenland. 
The  mineral  is  calcined  with  lime,  calcium  fluoride  and  alunii- 
nate  of  soda  being  formed. 

APFl6,6NaFl     +     6CaO     =     GCaFl2     +     Al203,3Na20 

Cryolite.  Calcium  fluoride.         Aluminate  of  soda. 

The  latter  compound  is  dissolved  out  by  water  and  decom- 
posed by  carbonic  acid  gas,  aluminium  oxide  being  precipitated 
and  sodium  carbonate  remaining  in  solution. 

Sodium  carbonate  crystallizes  in  oblique  rhombic  prisms, 
containing  10  molecules  of  water  of  crystallization.  When 
heated,  they  fuse  in  this  water  of  crystallization,  which  they 
then  abandon ;  they  also  lose  it  by  efflorescence  when  exposed 
to  the  air. 

Sodium  carbonate  is  very  soluble  in  water,  and  the  solution 
has  a  strongly  alkaline  reaction.  According  to  Poggiale, 

100  parts  of  water  at  0°    dissolve  7.08  parts  of  sodium  carbonate. 
10°         "       16.06  "  " 

20°         "      25.93  «  « 

25°         "       30.83  "  " 

30°         "       35.90  "  " 

104.6°      "       48.5  "  " 

The  saturated  solution  boils  at  104.6°.  Sodium  carbonate 
is  insoluble  in  alcohol. 

N* 


298  ELEMENTS   OF   MODERN   CHEMISTRY. 

Sodium  Acid  Carbonate,  NaHCO3. — When  carbonic  acid 
gas  is  passed  into  a  solution  of  sodium  carbonate  or  over 
crystals  of  that  salt,  the  gas  is  absorbed  and  sodium  acid  car- 
bonate, commonly  called  bicarbonate  of  soda,  is  formed.  This 
salt  crystallizes  in  oblique,  four-sided  prisms,  shortened  into  the 
form  of  tables.  Its  taste  is  salty  and  slightly  alkaline.  It  is 
less  soluble  in  water  than  the  neutral  carbonate.  It  restores 
the  blue  color  to  reddened  litmus ;  its  solution  does  not  pre- 
cipitate that  of  magnesium  sulphate.  When  boiled,  it  loses 
carbonic  acid,  neutral  carbonate  being  formed. 

PHOSPHATES   OF  SODIUM. 

There  are  three  phosphates  of  sodium  derived  from  ordinary 
or  otho-phosphoric  acid. 

H)  Na)  Na)  Na) 

PO4       H  V  PO4  +  2H20    Na  }•  PO*  +  12H20      Na  [  PO*  +  12H20 


H  I 
Hj 


HJ  Hj  Hj  NaJ 

Phosphoric     Monosodium         Disodium  phosphate.  Trisodium  phosphate, 

acid.  phosphate. 

Monosodium  phosphate  is  acid,  the  disodium  is  neutral,  and 
the  trisodium  has  an  alkaline  reaction.  Disodium  phosphate,  or, 
as  it  is  frequently  called,  common  or  neutral  phosphate  of  soda, 
is  the  most  important.  It  is  prepared  by  neutralizing  the  cal- 
cium acid  phosphate,  obtained  by  digesting  bone-dust  with  dilute 
sulphuric  acid  and  filtering,  with  sodium  carbonate.  Tricalcium 
phosphate  is  precipitated,  and  disodium  phosphate  remains  in 
solution.  By  evaporation  of  the  filtered  liquid,  the  salt  may 
be  obtained  in  voluminous,  transparent,  oblique  rhombic  prisms, 
containing  12  molecules  of  water  of  crystallization. 

SODIUM  BORATE,  OR  BORAX. 


This  salt  corresponds  to  a  boric  acid  containing  2Bo203  -f- 
H'O  =  H2Bo*07.  It  results  from  the  action  of  one  molecule 
of  sodium  oxide  upon  two  molecules  of  boric  oxide. 

2(Bo203)  -j-  Na20  =  Na2Bo407 

It  crystallizes  with  either  10  or  5  molecules  of  water. 
Borax  was  formerly  obtained  from  Asia,  where  it  exists  in 
solution  in  the  waters  of  certain  lakes.     By  the  evaporation 


LITHIUM.  299 

of  these  waters  a  product  known  as  tinkal  was  obtained ;  this 
is  natural  borax;  it  crystallizes  in  oblique  rhombic  prisms. 
Borax  is  found  in  abundance  in  certain  lakes  in  California. 
A  great  part  of  the  borax  of  commerce  is  obtained  by  satu- 
rating the  boric  acid  of  Tuscany  with  sodium  carbonate,  and 
causing  the  solution  to  crystallize  below  56°.  If  the  boiling 
solution  be  very  concentrated,  it  deposits  between  79  and  56° 
crystals  which  are  octahedral  and  contain  only  5  molecules 
of  water  of  crystallization.  The  two  varieties  of  borax,  the 
prismatic  and  the  octahedral,  differ  then  in  their  proportions 
of  water  of  crystallization. 

When  borax  is  heated,  it  melts  in  its  own  water,  swells  up 
and  becomes  dry,  and  then  undergoes  igneous  fusion.  Melted 
borax  dissolves  a  great  number  of  oxides  and  forms  with  them 
variously-colored  glasses  on  cooling.  It  dissolves  in  12  parts 
of  cold  and  2  parts  of  boiling  water  ;  the  solution  has  a  faint 
alkaline  reaction. 

Characters  of  Sodium  Salts. — Sodium  salts  are  not  pre- 
cipitated from  their  solutions  by  either  hydrogen  sulphide, 
ammonium  sulphide,  sodium  carbonate,  or  platinic  chloride. 
Hydrofluosilicic  acid  forms  with  them  a  white  precipitate.  A 
solution  of  potassium  antimonate  produces  a  white  precipitate 
of  sodium  antimonate  (Fremy). 

Sodium  salts  impart  a  yellow  color  to  flames. 

A  small  quantity  of  alcohol  may  be  ignited  in  a  saucer  and 
will  burn  with  an  almost  colorless  flame,  but  the  introduction 
of  a  small  quantity  of  sodium  hydrate,  chloride,  or  any  other 
sodium  compound,  at  once  colors  the  flame  bright  yellow. 

This  character  is  very  sensitive,  and  the  smallest  trace  of 
sodium  may  thus  be  recognized  by  introducing  a  platinum  wire, 
dipped  into  the  substance  to  be  tested,  into  the  colorless  flame 
of  the  blow-pipe  or  of  a  Bunsen  burner. 


LITHIUM. 

Li  =  7 

In  181*7,  Arfvedson,  a  Swedish  chemist,  discovered  a  new 
alkali,  lithia,  which  is  the  hydrate  of  lithium,  LiOH,  analogous 
to  potassium  hydrate,  KOH.  To  this  hydrate  corresponds  an 
oxide,  Li'2O,  and  a  chloride,  LiCl.  Bunsen  was  the  first  to  ob- 
tain the  metal  lithium,  which  he  prepared  by  electrolysis  of  the 


300  ELEMENTS    OF    MODERN    CHEMISTRY. 

fused  chloride.  It  is  a  silvery-white  metal,  but  its  surface  rap- 
idly tarnishes  in  the  air.  It  is  the  lightest  of  the  solid  ele- 
ments, its  density  being  between  0.578  and  0.589.  It  melts  at 
180°.  It  is  less  oxidizable  than  either  sodium  or  potassium. 
When  heated  above  its  point  of  fusion  in  the  air  or  in  oxygen, 
it  burns  with  a  brilliant  white  flame.  It  decomposes  water  at 
ordinary  temperatures,  but  without  melting  like  sodium. 

The  salts  of  lithium  are  soluble  in  water,  but  the  carbonate 
and  phosphate  only  slightly  so.  There  exists  also  a  double 
phosphate  of  sodium  and  lithium,  which  is  but  slightly  soluble. 
The  salts  of  lithium  communicate  a  red  color  to  the  flame  of 
alcohol  or  of  the  Bunsen  burner. 

The  compounds  of  lithium  are  generally  prepared  from  the 
native  silicate  known  as  lepidolite. 


(LE8IUM  AND  RUBIDIUM. 

SPECTRUM   ANALYSIS. 

Caesium  and  rubidium  are  two  alkaline  metals  discovered 
by  Kirchhoff  and  Bunsen  in  1860-61,  by  the  aid  of  a  new 
method  of  analysis.  This  method  consists  in  the  examination 
of  spectra ;  hence  the  name  spectrum  analysis. 

The  solar  spectrum  formed  upon  a  screen  which  intercepts  a 
beam  of  solar  light  refracted  by  passage  through  a  prism,  con- 
sists of  a  series  of  colored  bands.  The  different  simple  rays 
of  which  white  light  is  composed  are  unequally  refracted  by 
the  prism,  and  separate  from  each  other  on  their  emergence. 
The  violet  rays,  which  are  farthest  turned  from  their  primitive 
direction,  form  the  most  deviated  extremity  of  the  spectrum. 
The  red  rays,  which  are  the  least  refracted,  form  the  least  de- 
viated extremity.  The  visible  spectrum  of  solar  light  presents 
not  only  a  succession  of  variously-colored  bands ;  when  it  is 
closely  examined  by  the  aid  of  magnifying  instruments,  it  is 
found  that  the  succession  is  not  continuous,  but  that  the  lumi- 
nous bands  are  traversed  by  dark  lines.  These  lines,  which 
were  discovered  by  Wollaston  and  studied  by  Fraunhofer,  are 
very  numerous,  and  are  irregularly  distributed  throughout  the 
spectrum,  from  the  red  to  the  violet,  but  each  one  of  them 
occupies  a  definite  position,  and  for  the  principal  lines  that 
position  has  been  determined  by  exact  measurements.  Fraun- 


CESIUM    AND    RUBIDIUM.  301 

hofer  designated  them  by  the  letters  A,  B,  C,  D,  E,  F,  Gr,  H. 
The  D  line  is  the  most  distinct  of  all :  its  place  is  in  the  yel- 
low. Other  lights,  the  stars,  for  example,  give  similar  discon- 
tinuous spectra.  On  the  contrary,  an  incandescent  platinum 
wire,  or  any  other  luminous  source  which  contains  no  volatile 
matter,  gives  a  continuous  spectrum. 

Very  interesting  facts  are  observed  when  the  sources  of  light 
are  flames  into  which  the  vapors  of  volatile  substances,  par- 
ticularly the  metallic  salts,  are  introduced.  The  spectra  of  such 
flames  are  formed  exclusively  of  brilliant  lines  (see  plate). 

If  a  platinum  wire  which  has  been  dipped  into  a  solution 
of  sodium  chloride  be  introduced  into  the  colorless  flame  of 
a  Bunsen  burner,  the  flame  will  assume  a  yellow  color,  and  will 
give  a  visible  spectrum,  but  one  which  is  very  incomplete, 
since  it  consists  of  a  single  yellow  line.  It  has  been  found 
that  this  line  exactly  coincides  with  the  dark  line  D,  existing  in 
the  yellow  of  the  solar  spectrum.  This  line  characterizes 
sodium  in  all  of  its  compounds :  it  is  the  spectrum  of  sodium. 

In  the  same  manner,  a  flame  into  which  a  compound  of  potas- 
sium, lithium,  barium,  calcium,  or  other  volatile  metal  is  intro- 
duced, will  give  for  each  metal  a  particular  spectrum  formed  of 
variously-colored  lines.  Each  is  perfectly  characterized  by  the 
number,  color,  and  position  of  the  lines.  Barium  gives  the  most 
numerous  and  the  widest  lines  ;  other  metals  give  more  compli- 
cated spectra.  That  of  iron  is  composed  of  70  brilliant  lines. 

Kirchhoff  and  Bunsen,  who  discovered  these  facts,  made  a 
happy  application  of  them  to  analysis.  To  detect  the  presence 
of  a  metal  in  a  compound  or  even  in  a  mixture,  a  small  portion 
of  the  substance  is  introduced  into  a  colorless  gas  flame,  and 
the  spectrum  then  given  by  the  flame  is  observed  by  the  aid  of 
an  instrument  called  a  spectroscope. 

The  method  is  so  sensitive  that  -g-.oiru'.'UTrs'  °f  a  milligramme 
of  sodium  chloride  will  render  the  yellow  sodium  line  distinctly 
visible.  The  discovery  of  two  new  metals,  caesium  and  rubi- 
dium, crowned  the  brilliant  researches  of  Kirchhoff  and  Bunsen. 

Since  then,  three  other  new  metals  have  been  discovered  by 
the  aid  of  spectrum  analysis :  thallium,  which  gives  a  green 
line,  indium,  which  gives  an  indigo-blue  line,  and  gallium, 
which  gives  two  violet  lines  very  close  together.  Thallium  was 
discovered  by  Crookes  and  Lamy,  indium  by  Reich  and  Richter, 
and  gallium,  the  discovery  of  which  was  most  remarkable  of 
all,  by  Lecoq  de  Boisbaudran. 

26 


302  ELEMENTS   OF   MODERN    CHEMISTRY. 


THALLIUM. 

The  beautiful  green  line  given  by  this  metal  was  first  ob- 
served by  William  Crookes,  who  regarded  it  as  characteristic 
of  a  new  element.  The  honor  of  having  isolated  the  latter 
and  establishing  its  true  character  belongs  to  Lamy. 

Thallium  is  a  heavy  metal  which  resembles  lead  in  certain 
of  its  properties.  It  melts  at  200°;  its  density  is  11.9.  It 
forms  an  oxide,  TPO;  a  crystallizable  hydrate,  T10H,  which 
is  soluble  in  water  and  also  caustic ;  a  monochloride,  T1C1,  and 
a  moniodide,  Til.  These  compounds  relate  it  to  the  alkaline 
metals,  but  others,  which  include  an  oxide,  TPO3,  and  a  trichlo- 
ride, T1CP,  separate  it  from  that  class.  Its  principal  com- 
pounds have  been  studied  by  Lainy  and  Willm. 


BAEIUM 


Bunsen  obtained  barium  by  the  electrolysis  of  fused  barium 
chloride  ;  this  metal  is  very  avid  of  oxygen,  and  tarnishes 
rapidly.  It  decomposes  cold  water. 

Barium  Oxide,  or  Baryta,  BaO.  —  Barium  oxide  is  obtained 
by  calcining  barium  nitrate.  Its  nature  was  first  recognized 
in  1808,  by  Davy,  who  decomposed  it  by  the  voltaic  current. 
It  is  a  gray,  porous  substance,  which  unites  energetically  with 
water,  producing  a  hissing  noise  and  a  great  disengagement  of 
steam,  due  to  the  elevation  of  temperature.  The  product  of 
the  reaction  is  a  white  hydrate,  ordinarily  known  as  caustic 
baryta. 

BaO     +     H20     =     Ba(OH)2 

Barium  oxide.  Barium  hydrate. 

Barium  hydrate  is  soluble  in  two  parts  of  boiling  water,  and 
on  cooling  is  in  great  part  deposited  in  large  tabular  crystals, 
containing  8  molecules  of  water.  The  solution  of  barium  hy- 
drate in  water  is  called  baryta  water. 

Barium  Dioxide,  BaO2.  —  When  dry  oxygen  is  passed  over 
barium  oxide  heated  to  dull  redness,  the  gas  is  absorbed  and  a 
dioxide,  BaO2,  is  formed.  It  is  a  gray,  porous  mass,  some- 
times greenish.  It  loses  one  atom  of  oxygen  at  a  bright-red 
heat.  When  brought  in  contact  with  water,  it  combines  with 


BARIUM    SALTS.  303 

the  latter  quietly  and  without  disengagement  of  heat,  forming 
a  pulverulent  hydrate. 

When  treated  with  sulphuric  acid,  barium  dioxide  disen- 
gages oxygen  mixed  with  ozone.  When  its  hydrate  is  intro- 
duced into  hydrochloric  acid,  hydrogen  dioxide  is  formed. 

Barium  Sulphide,  BaS. — This  is  obtained  by  reducing 
barium  sulphate  with  charcoal. 

BaSO*       +     C4     =       BaS       +     4CO 

Barium  sulphate.  Barium  sulphide. 

The  sulphate  is  reduced  to  fine  powder,  and  is  mixed  with  a 
certain  quantity  of  flour  or  rosin.  The  mixture  is  then  made 
into  a  paste  with  linseed  oil,  and  shaped  into  little  balls.  These 
are  calcined  at  a  bright-red  heat  in  a  covered  crucible,  and  a 
porous,  gray  mass  is  thus  obtained  which,  when  treated  with 
boiling  water,  yields  a  solution  which  deposits  hexagonal  tables 
after  filtration  and  cooling.  These  crystals  do  not  present  a 
very  constant  composition :  it  is  a  mixture  of  sulphide,  sulphy- 
drate,  and  hydrate  of  barium.  Their  solution  has  a  light-yel- 
low color. 

BARIUM    SALTS. 

Barium  Chloride,  BaCl2  -J-  2H20. — This  salt  is  obtained 
by  saturating  the  solution  of  barium  sulphide  with  hydrochloric 
acid.  Hydrogen  sulphide  is  disengaged ;  the  solution  is  boiled, 
filtered,  and  evaporated  to  crystallization.  Barium  chloride 
separates  in  quadrangular  tables  belonging  to  the  type  of  the 
right  rhombic  prism.  These  crystals  are  inalterable  in  the  air. 
100  parts  of  water  at  18°  dissolve  43.5  parts  of  barium  chlo- 
ride, and  78  parts  at  105.5°,  the  temperature  of  ebullition  of 
the  saturated  solution  (Gay-Lussac).  Absolute  alcohol  dis- 
solves ^Lg-  of  its  weight  of  barium  chloride. 

Barium  Nitrate,  Ba(N03)2. — Barium  nitrate  is  prepared 
by  decomposing  barium  sulphide  or  carbonate  with  dilute  nitric 
acid,  and  filtering  and  evaporating  the  solution. 

It  crystallizes  in  regular  octahedra,  or  in  cubo-octahedra. 
The  crystals  are  transparent  and  unaltered  in  the  air.  One 
part  of  this  salt  requires  for  its  solution  20  parts  of  water  at 
0.12°;  5  parts  of  water  at  15°;  2.8  parts  at  106°,  the  tem- 
perature of  ebullition  (Gay-Lussac).  When  heated  to  redness, 
barium  nitrate  gives  off  oxygen,  nitrogen,  and  red  vapors, 
leaving  a  residue  of  oxide,  BaO. 


304  ELEMENTS   OP   MODERN   CHEMISTRY. 

Barium  Sulphate,  BaSO. — This  salt  is  found  abundantly 
in  nature  as  heavy  spar,  and  sometimes  occurs  in  right  rhom- 
bic crystals.  It  is  entirely  insoluble  in  water  and  acids,  with 
the  exception  of  concentrated  sulphuric  acid.  It  is  precipi- 
tated as  a  finely-divided,  amorphous  powder  when  sulphuric 
acid  or  a  soluble  sulphate  is  added  to  a  solution,  even  very  di- 
lute, of  a  salt  of  barium. 

Barium  Carbonate,  BaCO3. — Barium  carbonate  constitutes 
an  amorphous,  white  powder,  which  is  obtained  by  double  de- 
composition on  adding  solution  of  sodium  carbonate  to  a  solu- 
tion of  barium  sulphide.  Natural  barium  carbonate  is  an 
abundant  mineral,  and  is  found  crystallized  in  right  rhombic 
prisms ;  it  is  called  witherite. 

Characters  of  Barium  Salts. — Barium  salts  are  precipi- 
tated neither  by  hydrogen  sulphide  nor  by  ammonium  sulphide. 
Sodium  carbonate  produces  in  them  a  white  precipitate.  Even 
when  very  dilute,  the  barium  salts  produce  a  white  precipitate 
with  sulphuric  acid,  which  is  insoluble  in  either  cold  or  boiling 
nitric  acid. 

STRONTIUM. 

Sr  =  87.5 

The  compounds  of  this  metal  present  great  analogies  to  those 
of  barium. 

Strontium  was  discovered  by  Davy  in  1808,  but  the  metal 
was  isolated  by  Bunsen  and  Matthiessen  by  the  aid  of  a  process 
similar  to  that  which  serves  for  the  preparation  of  barium. 
Matthiessen  describes  it  as  a  yellow  metal,  having  a  density  of 
2.50-2.58,  harder  than  lead,  and  decomposing  cold  water. 

Strontium  forms  two  oxides,  a  monoxide,  SrO,  and  a  dioxide, 
SrO2. 

Strontium  chloride,  SrCl2,  crystallizes  in  deliquescent  needles 
which  contain  three  molecules  of  wafer  of  crystallization.  It 
is  very  soluble  in  water  and  slightly  soluble  in  alcohol ;  the 
alcoholic  solution  burns  with  a  red  flame. 

Strontium  nitrate,  Sr(N03)2,  which  is  prepared  like  barium 
nitrate,  is  deposited  from  its  hot  aqueous  solution  in  anhydrous 
octahedra,  and  crystallizes  at  low  temperatures  in  oblique  rhom- 
bic tables  containing  5  molecules  of  water  of  crystallization 
(Laurent). 

The  carbonate  of  strontium,  SrCO3  (strontianite),  and  the 


CALCIUM.  305 

sulphate,  SrSO4  (celestine),  are  found  native.  These  two  salts 
are  insoluble  in  water,  and  are  deposited  as  white  precipitates 
on  adding  a  soluble  carbonate  or  sulphate  to  the  solution  of  a 
strontium  salt.  Strontium  sulphate  is  less  insoluble,  however, 
than  barium  sulphate. 


CALCIUM. 

Ca  =  40 

Lime,  which  is  universally  known,  is  the  oxide  of  a  metal 
called  calcium.  According  to  Lies-Bodard  and  Jobin,  calcium 
may  be  obtained  by  decomposing  calcium  iodide  with  sodium 
in  an  iron  crucible.  Matthiessen  obtained  it  by  decomposing 
fused  calcium  chloride  by  the  voltaic  current. 

Calcium  has  a  yellow  color  when  freshly  filed,  but  it  tarnishes 
rapidly  in  moist  air  and  becomes  covered  with  a  grayish  layer 
of  hydrate.  When  heated  upon  platinum-foil,  it  takes  fire  and 
burns  with  a  dazzling  flame.  It  decomposes  water  at  ordinary 
temperatures. 

OXIDE  AND  HYDRATE  OF   CALCIUM. 

Lime,  or  calcium  oxide,  CaO.  is  obtained  by  calcining  the 
carbonate  in  peculiar  furnaces,  which  are  called  lime-kilns.  It 
occurs  as  large,  compact,  and  hard  grayish  masses,  which  con- 
stitute quick-lime. 

It  is  infusible,  even  at  the  highest  temperatures.  When 
exposed  to  the  air,  it  attracts  moisture  and  carbonic  acid,  aug- 
ments in  volume,  and  is  finally  converted  into  a  white  powder, 
a  mixture  of  calcium  hydrate  and  carbonate.  When  lime  is 
sprinkled  with  water,  it  absorbs  the  liquid  without  giving  rise 
to  any  particular  phenomenon ;  but  in  a  little  while,  the  pieces 
saturated  with  water  become  hot,  give  off  steam,  and  then  they 
split  and  increase  in  volume.  If  enough  water  be  used,  the 
quick-lime  will  be  converted  into  a  white  powder,  which  is 
called  slaked  lime;  it  is  calcium  hydrate. 

CaO  +  H20  =  Ca02H2  =  Ca(OH)2 

When  slaked  lime  is  suspended  in  water,  a  white,  creamy 
liquid  is  obtained  that  is  called  milk  of  lime.  If  this  be  fil- 
tered or  allowed  to  settle,  the  clear,  limpid  liquid  resulting  will 
have  an  alkaline  reaction,  for  it  contains  a  small  quantity  of 

26* 


306  ELEMENTS   OP   MODERN   CHEMISTRY. 

calcium  hydrate  in  solution :  it  is  lime-water.  Calcium  hydrate 
is  more  soluble  in  cold  than  in  hot  water. 

Employment  of  Lime  in  Constructions. — Lime  is  largely 
employed  for  building  purposes  in  both  ordinary  and  submarine 
constructions.  The  limestone  which  is  used  for  the  preparation 
of  lime  is  rarely  pure,  and  consequently  the  product  of  its  cal- 
cination presents  different  qualities,  according  to  the  propor- 
tions of  foreign  matters  which  remain  in  the  lime,  and  which 
consist  of  a  small  quantity  of  magnesia,  oxide  of  iron,  and 
especially  clay.  Fat  limes  are  those  produced  by  the  calcina- 
tion of  almost  pure  limestones;  they  develop  much  heat,  and 
swell  up  very  much  on  slaking.  Such  lime  forms  an  unctuous 
and  binding  paste  with  water,  and  forms  ordinary  mortar  when 
mixed  with  sand.  Impure  linrestones  yield  lean  lime,  contain- 
ing magnesia,  oxide  of  iron,  and  clay.  It  is  gray,  and  develops 
but  little  heat  and  increases  but  slightly  in  volume  on  slaking. 
The  calcination  of  limestone  containing  from  10  to  30  per  cent, 
of  clay  produces  hydraulic  lime.  Such  lime  sets  under  water, 
that  is,  the  mortar  solidifies  after  a  few  days,  and  becomes  very 
hard,  even  when  immersed  in  water.  On  account  of  this  curious 
property  it  is  used  in  submarine  constructions.  Such  lime  is 
yellow ;  slaking  it  produces  but  little  heat,  and  scarcely  any  in- 
crease in  volume.  The  hydraulic  mortar  formed  by  its  mix- 
ture with  sand  will  harden  under  water.  Mortars  possessing 
this  property  may  also  be  prepared  by  mixing  lime  with  baked 
argillaceous  materials,  such  as  powdered  tiles,  pottery,  bricks, 
etc.  Certain  argillaceous  rocks  of  volcanic  origin,  the  pozzolana 
so  abundant  near  Vesuvius,  for  example,  yield  an  excellent 
hydraulic  lime  when  mixed  with  fat  lime. 

Cement  is  a  variety  of  lime  resulting  from  the  calcination  of 
limestones  containing  from  40  to  50  per  cent,  of  slate.  When 
mixed  with  water,  such  cement  sets  in  a  few  minutes  in  a  solid 
mass  like  plaster.  Vicat  has  shown  that  the  different  varieties 
of  hydraulic  lime  and  cement  can  be  prepared  by  properly 
calcining  carbonate  of  lime,  or  chalk,  with  various  proportions 
of  clay.  According  to  him,  ordinary  mortar  sets  because  the 
lime  gradually  absorbs  carbonic  acid  gas  from  the  air,  forming 
a  carbonate  which  hardens  and  binds  together  the  grains  of 
sand.  The  hardening  of  hydraulic  lime  and  mortar  is  due  to 
another  cause :  the  clay  which  they  contain  in  the  anhydrous 
state  tends  to  become  hydrated  and  to  form  a  double  silicate  of 
calcium  and  aluminium,  or  a  silicate  and  aluminate  of  calcium, 


CALCIUM    CHLORIDE — CALCIUM    NITRATE.  307 

insoluble  compounds,  which  become  very  coherent  on  contact 
with  water. 

CALCIUM   CHLORIDE. 

CaCl2 

This  salt  is  prepared  by  dissolving  white  marble  or  chalk  in 
hydrochloric  acid.  When  the  solution  is  concentrated  it  deposits 
large,  six-sided  prisms,  containing  6  molecules  of  water  of  crys- 
tallization. They  are  very  deliquescent  and  produce  a  depres- 
sion of  temperature  when  they  are  dissolved  in  water.  If  they 
be  mixed  with  their  own  weight  of  snow  or  powdered  ice,  a 
cold  of  — 45°  may  be  produced. 

When  they  are  heated,  they  melt  in  their  water  of  crystalliza- 
tion, of  which  they  lose  4  molecules  at  200°,  and  the  remainder 
at  a  red  heat ;  at  the  latter  point  the  mass  enters  into  igneous 
fusion.  On  cooling,  the  fused  calcium  chloride  solidifies  to  a 
white,  crystalline  mass,  in  which  form  it  is  ordinarily  employed 
for  the  desiccation  of  gases. 

Calcium  chloride  dissolves  readily  in  alcohol. 

CALCIUM   NITRATE. 

Ca(NO3)2  -f  4H2O 

This  salt  is  formed  naturally  in  the  neighborhood  of  dwell- 
ings, in  the  soils  of  cellars,  and  in  damp  walls.  It  is  contained 
in  what  are  known  as  saltpetre  materials ;  it  exists  in  certain 
spring  and  well  waters.  It  may  be  made  by  saturating  nitric 
acid  with  calcium  carbonate.  It  is  very  soluble  in  water  and 
in  alcohol.  It  crystallizes  with  difficulty  in  six-sided,  oblique 
rhombic  prisms,  which  contain  4  molecules  of  water  of  crys- 
tallization :  they  are  deliquescent. 

CALCIUM   CARBONATE. 

(CARBONATE  OF  LIME.) 
CaCO3 

Calcium  carbonate  is  found  in  great  abundance  in  nature, 
and  under  different  forms.  It  exists  crystallized  as  Iceland 
spar  and  aragonite  ;  the  former  crystallizes  in  colorless,  trans- 
parent, and  doubly  refracting  rhombohedra  ;  the  latter  in  right 
rectangular  prisms. 


308  ELEMENTS    OF    MODERN    CHEMISTRY. 

Marble,  the  various  limestones,  and  chalk,  constitute  other 
varieties  of  natural  calcium  carbonate.  Pure  water  dissolves 
but  feeble  traces  of  this  salt;  water  charged  with  carbonic 
acid  dissolves  a  larger  quantity,  converting  it  into  dicarbonate. 
It  is  in  this  state  that  it  is  contained  in  hard  waters. 

Calcium  carbonate  may  be  prepared  by  double  decomposition 
between  solutions  of  sodium  carbonate  and  calcium  chloride. 
When  heated  to  bright  redness,  it  is  completely  decomposed 
into  lime  and  carbonic  anhydride. 


CALCIUM  SULPHATE. 

CaSO* 

This  salt  exists  in  two  states  in  nature :  anhydrous,  it  con- 
stitutes the  anhydrite  of  mineralogists ;  combined  with  two 
molecules  of  water  of  crystallization,  it  forms  gypsum  or  plas- 
ter stone.  Gypsum  sometimes  occurs  in  lance-head-shaped 
crystals,  grouped  together  ;  they  are  divisible  into  thin,  trans- 
parent layers,  easily  scratched  by  the  finger-nail.  Certain 
varieties  of  gypsum  constitute  alabaster.  All  the  forms  of 
hydrated  calcium  sulphate  contain  21  per  cent,  of  water. 

When  heated  to  80°  in  the  air,  or  to  115°  in  closed  vessels, 
the  sulphate,  CaSO4  -f  2H20,  abandons  its  water  of  crystalli- 
zation and  is  converted  into  the  anhydrous  sulphate.  Between 
120  and  130°,  this  dehydration  is  rapid  and  complete.  It  is 
operated  on  the  large  scale  in  plaster  furnaces.  In  this  state 
calcium  sulphate  will  readily  recombine  with  its  water  of 
crystallization.  If  the  plaster  be  calcined  at  too  high  a  tem- 
perature it  will  not  again  become  hydrated. 

If  powdered  plaster  of  Paris  be  mixed  with  enough  water 
to  form  a  creamy  liquid,  it  may  be  poured  into  a  mould,  and 
in  a  few  minutes  will  harden  to  a  compact  mass,  completely 
filling  every  cavity  of  the  mould.  In  becoming  hydrated,  the 
particles  of  calcium  sulphate  assume  the  crystalline  form  and 
increase  in  volume.  These  properties  render  plaster  of  Paris 
valuable  in  building  operations. 

It  is  also  employed  to  a  large  extent  in  agriculture. 

Calcium  sulphate  is  but  slightly  soluble  in  water.  1000 
parts  of  boiling  water  dissolve  a  little  more  than  2  parts  of 
the  salt;  at  35°  they  dissolve  2.64  parts;  at  20°,  2.05  parts. 


CALCIUM    HYPOCHLORITE. 


309 


CALCIUM    HYPOCHLORITE. 

Ca(ClO)2 

Calcium  hypochlorite  exists  in  a  product  largely  employed 
in  the  arts  under  the  name  of  chloride  of  lime,  and  which  is 
obtained  by  exposing  well-hydrated  lime  to  the  action  of  chlo- 
rine ;  it  is  a  mixture  of  calcium  chloride  and  calcium  hypo- 
chlorite. 


4C1 


2CaO     =       CaCP       +       Ca(ClO)2 

Calcium  chloride.      Calcium  hypochlorite. 


The  operation  is  conducted  by  passing  a  current  of  chlorine 
over  slaked  lime  placed  in  thin  layers  upon  shelves  arranged 
in  the  walls  of  masonry  chambers.  The  chlorine  is  made  in 
earthenware  vessels,  A  (Fig.  101),  heated  in  a  water-bath;  it 


FIG.  101. 

is  washed  in  the  jars  D,  and  then  conducted  into  the  upper 
part  of  the  chamber  by  the  tube  G.  In  order  to  insure  the 
preservation  of  the  chloride  of  lime,  an  excess  of  lime  is  always 
left  in  it. 


310  ELEMENTS   OF   MODERN   CHEMISTRY. 

Chloride  of  lime  is  a  powerful  bleaching  agent ;  it  owes  this 
property  to  the  calcium  hypochlorite  which  it  contains,  and 
which  is  decomposed  by  the  action  of  acids. 

If  hydrochloric  acid  be  added  to  a  solution  of  chloride  of 
lime,  chlorine  gas  is  at  once  disengaged  with  effervescence. 
The  reaction  may  be  conceived  to  take  place  in  two  phases. 
The  hydrochloric  acid  acts  upon  the  hypochlorite,  forming 
hypochlorous  acid. 

2HC1     +      Ca(ClO)2      =      CaCP      +      2HC10 

Calcium  hypochlorite.     Calcium  chloride.    Hypochlorous  acid. 

The  hypochlorous  acid  thus  set  free  then  reacts  with  the 
calcium  chloride,  forming  calcium  hydrate  and  chlorine. 

CaCP  +  2HC10  =  Ca(OH)2  -f  2C12 

The  calcium  hydrate  is  in  the  presence  of  an  excess  of  hy- 
drochloric acid,  by  which  it  is  reconverted  into  calcium  chlo- 
ride. The  latter  salt  is  thus  continually  decomposed  and 
re-formed. 

Chloride  of  lime  is  also  decomposed  by  less  energetic  acids, 
even  by  carbonic  acid  gas. 

When  a  solution  of  chloride  of  lime  is  boiled,  the  hypochlo- 
rite which  it  contains  is  converted  into  chlorate  and  chloride. 

3Ca(C10)2     =     Ca(C103)2     +     2CaCP 

Calcium  hypochlorite.        Calcium  chlorate. 

Characters  of  Calcium  Salts. — Calcium  salts  are  not  pre- 
cipitated either  by  hydrogen  sulphide  or  ammonium  sulphide. 
Sodium  carbonate  forms  in  them  a  white  gelatinous  precipitate. 
Sulphuric  acid  and  the  soluble  sulphates  produce  a  white  pre- 
cipitate, if  the  calcium  solutions  be  concentrated  or  only  mod- 
erately dilute.  Oxalic  acid,  or  better,  ammonium  oxalate, 
produces  a  white  precipitate  of  calcium  oxalate,  even  in  the 
most  dilute  solutions  of  calcium  salts. 


MAGNESIUM. 


Magnesium  was  discovered  by  Bussy.  Matthiessen  obtained 
it  by  decomposing  fused  magnesium  chloride  by  electricity. 

Preparation.  —  Deville  and  Caron  recommend  the  following- 
process  for  the  preparation  of  considerable  quantities  of  mag- 


MAGNESIUM    OXIDE — MAGNESIUM    CHLORIDE.          311 

nesium.  A  mixture  of  600  grammes  of  anhydrous  magnesium 
chloride,  100  grammes  of  sodium  chloride,  100  grammes  of 
calcium  fluoride,  and  100  grammes  of  sodium  cut  into  small 
pieces  is  heated  to  redness  in  a  covered  crucible.  The  magne- 
sium chloride  is  reduced  by  the  sodium,  and  the  magnesium 
set  free  collects  in  little  globules  disseminated  in  the  fused 
mass,  which  must  be  stirred  with  an  iron  rod.  These  little 
globules  are  removed  from  the  scoriae  when  cold,  introduced 
into  a  charcoal  boat,  and  heated  to  bright  redness  in  a  current 
of  hydrogen.  The  magnesium  volatilizes  and  condenses  far- 
ther on  in  the  tube ;  it  may  then  be  fused  with  a  flux  consisting 
of  magnesium  chloride,  sodium  chloride,  and  calcium  fluoride. 
The  metal  collects  at  the  bottom  of  the  crucible. 

Properties, — Magnesium  has  a  density  of  1.74  or  1.75.  It 
fuses  at  500°.  It  decomposes  water  at  ordinary  temperatures 
but  slowly.  It  may  readily  be  rolled  into  ribbon  or  drawn  into 
wire.  The  wire  is  grayish  and  not  very  brilliant.  The  end 
of  a  bundle  of  these  wires  may  be  heated  in  an  alcohol  lamp 
until  they  take  fire,  and  the  whole  may  then  be  plunged  into  a 
jar  of  oxygen.  They  burn  with  an  incomparable  splendor  that 
the  eye  cannot  support;  at  the  same  time  the  jar  becomes  filled 
with  a  white  smoke,  which  condenses  into  a  white  powder,  the 
product  of  the  combustion  ;  it  is  magnesia,  the  oxide  of  mag- 
nesium. 

MAGNESIUM   OXIDE,   OR  MAGNESIA. 
MgO 

This  body  is  obtained  by  calcining  white  magnesia,  or  mag- 
nesium hydrocarbonate.  It  is  a  white,  infusible,  light,  and 
insipid  powder.  It  does  not  dissolve  in  water,  but  combines 
with  that  liquid  forming  a  hydrate,  Mg(OH)2  =  MgO.H'O. 
This  hydrate  slowly  restores  the  blue  color  to  reddened  litmus- 
paper. 

Magnesium  hydrate  is  precipitated  when  a  solution  of  caustic 
potassa  is  added  to  the  solution  of  a  magnesium  salt. 

Calcined  magnesia  is  frequently  employed  in  medicine. 

MAGNESIUM   CHLORIDE. 

MgCP 

This  salt  is  known  in  the  anhydrous  state  and  crystallized. 
Anhydrous  magnesium  chloride  is  prepared  by  dissolving  the 


312  ELEMENTS   OF   MODERN    CHEMISTRY. 

carbonate  in  hydrochloric  acid,  adding  ammonium  chloride  to 
the  solution  and  evaporating  to  dryness.  A  double  chloride  of 
magnesium  and  ammonium  is  thus  obtained  which  may  be  per- 
fectly dried ;  the  dry  mass  is  introduced  into  a  clay  crucible  and 
heated;  the  ammonium  chloride  volatilizes,  while  the  magne- 
sium chloride  remains,  and  solidifies  on  cooling  to  a  colorless, 
pearly  mass. 

It  is  very  soluble  in  water,  and  when  properly  concentrated, 
the  solution  deposits  deliquescent,  prismatic  crystals  containing 
six  molecules  of  water  of  crystallization.  These  crystals  can- 
not be  dehydrated,  nor  can  their  solution  be  evaporated  to 
dryness,  without  decomposing  the  chloride  by  the  action  of  the 
water;  under  these  circumstances  the  magnesium  chloride  is 
converted  into  hydrochloric  acid  and  magnesia. 

MgCP  +  H20  =  2HC1  +  MgO 

MAGNESIUM   CARBONATE. 

MgCO3 

The  anhydrous  carbonate  MgCO3  (giobertite,  magnesite)  is 
found  native,  crystallized  in  rhombohedra,  similar  to  those  of 
calcium  carbonate.  Considerable  deposits  are  also  found  of  a 
double  carbonate  of  magnesium  and  calcium,  known  as  dolomite. 

When  a  boiling  solution  of  magnesium  sulphate  is  precipi- 
tated by  an  excess  of  sodium  carbonate,  carbonic  acid  gas  is 
disengaged,  and  a  precipitate  is  formed  containing  at  the  same 
time  magnesium  carbonate  and  magnesium  hydrate  (magnesium 
hydrocarbonate) . 

When  this  is  dried,  it  constitutes  the  white  magnesia  of  the 
pharmacies. 

MAGNESIUM  SULPHATE. 

MgSO*  +  7H20 

This  salt  exists  in  solution  in  sea- water  and  in  certain  purga- 
tive mineral  waters,  such  as  those  of  Sedlitz,  in  Bohemia,  and 
Epsom,  in  England.  Hence  the  names  Sedlitz  salt  and  Epsom 
salt,  formerly  given  to  this  body. 

At  Stassfurth,  it  is  found  crystallized  with  one  molecule  of 
water  (kieserite)  and  mixed  with  the  anhydrous  sulphate. 

It  is  deposited  from  the  mother-liquors  of  salt-marshes  when 
they  are  evaporated  at  the  natural  summer  heat  (Balard). 

When  it  separates  at  ordinary  temperatures  from  an  aqueous 


ALUMINIUM.  313 

solution  that  has  been  tolerably  concentrated  by  heat,  it  crystal- 
lizes in  transparent  and  colorless  right  rhombic  prisms.  At 
0°,  it  crystallizes  with  12  molecules  of  water ;  at  30°,  with  6 
molecules; 

Its  taste  is  disagreeable,  at  the  same  time  salty  and  bitter. 
When  magnesium  sulphate  crystallized  with  7  molecules  of 
water  is  heated,  it  first  melts  in  its  water  of  crystallization,  of 
which  it  loses  6  molecules.  At  132°,  it  still  retains  one  mole- 
cule, which  it  loses  only  at  210°. 

It  is  very  soluble  in  water;  100  parts  of  water  at  0°  dis- 
solve 25.76  parts  of  the  anhydrous  sulphate,  and  0.47816 
part  for  every  additional  degree  (Gray-Lussac). 

Magnesium  sulphate  forms  a  double  sulphate  with  potassium 
sulphate,  K2S04.MgS04  +  6H2O. 

Characters  of  Magnesium  Salts. — They  are  precipitated 
by  neither  hydrogen  sulphide  nor  ammonium  sulphide.  Sodium 
carbonate  produces  a  white,  flocculent  precipitate.  Potassium 
hydrate  and  ammonia  form  white  precipitates,  but  ammonia 
will  not  precipitate  magnesia  from  an  acid  solution  or  from  one 
containing  ammonium  chloride.  Sodium  phosphate  and  ammonia 
together  produce  a  granular  precipitate  of  ammonio-magnesium 
phosphate. 

ALUMINIUM. 

Al  -=  27  5 

This  metal  long  remained  a  chemical  curiosity,  and  has  only 
become  common  within  a  few  years.  It  was  discovered  in 
1827  by  Wohler,  and  in  1854,  H.  Saint-Claire  Deville  succeeded 
in  producing  it  on  the  large  scale.  It  is  obtained  by  decom- 
posing aluminium  and  sodium  double  chloride  by  sodium. 

AFCl6,2NaCl  +  3Na2  =  8NaCl  +  AP 

In  the  arts,  a  mixture  of  sodium,  aluminium  and  sodium 
double  chloride,  and  cryolite,  is  projected  into  a  reverberatory 
furnace  heated  to  bright  redness.  The  cryolite  acts  as  a  flux  : 
it  is  a  double  fluoride  of  sodium  and  aluminium,  found  native 
in  Greenland. 

Aluminium  is  a  white  metal,  and  has  a  somewhat  bluish 
lustre  when  polished.     It  is  ductile,  malleable,  very  sonorous, 
and  a  good  conductor  of  heat  and  electricity.     It  is  as  light  as 
glass  and  porcelain,  its  density  being  only  2.56. 
o  27 


314  ELEMENTS    OF    MODERN   CHEMISTRY. 

Aluminium  is  unaltered  by  the  air,  even  by  moist  air.  When 
heated  in  thin  sheets  in  a  current  of  oxygen,  it  burns  and  is 
converted  into  alumina.  Nitric  and  sulphuric  acids  scarcely 
attack  it.  Hydrochloric  acid  dissolves  it  rapidly,  disengaging 
hydrogen.  It  is  immediately  attacked  by  boiling  solutions  of 
potassium  or  sodium  hydrates;  hydrogen  is  disengaged  and 
alkaline  aluminates  are  formed. 


ALUMINIUM   OXIDE,  OR  ALUMINA. 

A12O3 

Corundum,  a  very  hard  precious  stone,  consists  of  anhydrous 
alumina.  It  is  named  oriental  ruby  when  it  has  a  red  color ; 
sapphire  when  it  is  blue,  and  oriental  topaz  when  it  has  a 
yellow  tint.  Emery  is  a  sort  of  opaque  corundum  ;  it  is  gran- 
ular and  colored  by  a  small  quantity  of  oxide  of  iron. 

When  ammonium  carbonate  is  added  to  a  solution  of  alum, 
carbon  dioxide  is  evolved,  and  a  gelatinous  precipitate  of  hy- 
drated  alumina  is  formed. 

The  precipitate  dissolves  readily  in  caustic  potassa.  When 
heated,  it  loses  water  and  is  converted  into  anhydrous  alumina ; 
the  latter  is  undecomposable  by  heat ;  it  fuses  only  in  the  flame 
of  the  oxy hydrogen  blow-pipe.  Gaudin  has  succeeded  in  pro- 
ducing fine  precious  stones  that  cannot  be  cut  by  the  file,  and 
at  least  as  hard  as  rock-crystal,  by  melting  Limoge  emerald 
(anhydrous  alumina)  with  various  substances,  such  as  sand, 
kaolin,  talc,  and  lime,  which  are  added  as  fluxes. 

Alumina  cannot  be  reduced  by  charcoal  at  the  highest  tem- 
peratures ;  it  can  only  be  reduced  by  the  joint  action  of  char- 
coal and  chlorine ;  aluminium  chloride  is  then  formed. 

ALUMINIUM   CHLORIDE. 

A12C1« 

When  a  current  of  chlorine  is  passed  over  an  incandescent 
mixture  of  alumina  and  charcoal,  aluminium  chloride  and 
carbon  monoxide  are  formed  (Oersted). 

APO3  +  3C  +  Cl6  =  SCO  -f  APC16 

Aluminium  chloride  thus  formed  is  a  white,  crystalline  sub- 
stance, sometimes  having  a  light-yellow  color.  It  is  fusible,  and 


ALUMINIUM    SULPHATE — ALUM.  315 

volatilizes  in  the  air  at  a  temperature  little  above  100°.  When 
exposed  to  the  air  it  gives  off  white  fumes  and  attracts  moist- 
ure. It  dissolves  in  water  with  production  of  heat. 

A  solution  of  aluminium  chloride  may  be  obtained  by  dis- 
solving gelatinous  alumina  in  hydrochloric  acid.  When  this 
solution  is  evaporated,  it  decomposes  as  soon  as  it  attains  a 
certain  degree  of  concentration,  disengaging  hydrochloric  acid, 
and  leaving  alumina. 

Aluminium  chloride  readily  combines  with  sodium  chloride, 
forming  a  double  chloride,  APCl6.2NaCl,  fusible  towards  200°. 

ALUMINIUM   SULPHATE. 

A12(SO)3  -f  18H2O 

This  is  obtained  in  the  arts  by  decomposing  non-ferruginous 
clays  with  sulphuric  acid.  It  crystallizes  with  difficulty  in 
needles  and  in  thin,  pearly  scales.  In  this  state  it  contains  18 
molecules  of  water  of  crystallization.  It  dissolves  in  2  parts 
of  cold  water.  When  heated,  it  first  loses  its  water,  and  at  a 
higher  temperature  it  gives  off  sulphuric  anhydride,  leaving  a 
residue  of  alumina. 

AP(S04)3  =  3S03  +  APO3 

It  is  seen  that  aluminium  sulphate  represents  3  molecules 
of  sulphuric  acid,  in  which  the  6  atoms  of  hydrogen  have  been 
replaced  by  the  hexatomic  couple  AP. 

H2SOM  (SO4 

H2S04  f-  +  APO3  ==  3H20  -f  (AP)*  1  SO* 
H2S04)  (.SO4 

ALUMINIUM    AND    POTASSIUM    DOUBLE    SUL- 
PHATE,  OR  ALUM. 

A12(SO4)3.K2SO*  -f  24H2O 

If  a  concentrated  solution  of  aluminium  sulphate  be  added 
to  a  concentrated  solution  of  potassium  sulphate,  and  the  mix- 
ture be  stirred  with  a  glass  rod,  a  crystalline  deposit  soon  forms 
from  the  union  of  the  two  salts  to  form  a  double  sulphate 
which  is  alum. 

This  salt  is  not  very  soluble  in  cold  water,  but  dissolves 
abundantly  in  boiling  water,  and  is  deposited  on  cooling  in 


316  ELEMENTS   OP   MODERN   CHEMISTRY. 

voluminous,  transparent  octahedra.  When  heated,  these  crys- 
tals melt  in. their  water  of  crystallization  (24  molecules),  and 
in  losing  this  water,  the  melted  mass  swells  up  considerably. 
Alum  may  be  obtained  crystallized  in  cubes,  and  it  is  prepared 
in  this  form  in  the  neighborhood  of  Civita-Vecchia  by  working 
a  mineral  which  contains  the  elements  of  alum  with  a  large 
excess  of  alumina.  The  mineral  is  known  as  aluminite,  and  the 
cubical  alum  is  called  Roman  alum. 

This  cubical  variety  may  be  prepared  in  the  laboratory  by 
adding  a  small  quantity  of  potassium  carbonate  to  a  hot  solu- 
tion of  ordinary  alum,  so  that  the  precipitate  first  formed  will 
be  redissolved  on  agitating  the  liquid.  On  cooling,  cubical 
crystals  are  deposited  which  are  ordinarily  opaque.  These  are 
formed  under  the  influence  of  a  small  quantity  of  basic  sul- 
phate (aluminium  sulphate  combined  with  an  excess  of  alu- 
mina) contained  in  the  liquid,  and  which  probably  enters  into 
the  constitution  of  the  crystals.  With  this  slight  difference, 
octahedral  alum  and  cubical  alum  present  the  same  composi- 
tion, which  is  expressed  by  the  formula  A12(S04)3.K2SO*  -f 
24H20. 

Ammonia  alum  is  obtained  by  adding  ammonium  sulphate 
to  solution  of  aluminium  sulphate.  It  possesses  a  constitution 
analogous  to  that  of  ordinary  alum,  with  which  it  is  isomor- 
phous.  It  contains 

AP(S04)3.(NH4)2S04  -f  24H20 

It  is  often  substituted  in  the  arts  for  potassium  alum,  being 
cheaper  than  the  latter. 

When  strongly  calcined,  it  leaves  a  residue  of  pure  alumina. 

Other  alums  are  known  in  which  iron,  manganese,  and  chro- 
mium play  the  part  taken  by  aluminium  in  ordinary  alum. 
These  alums  are  all  isomorphous  (Mitseherlich).  By  the  ac- 
tion of  sulphuric  acid  on  the  sesquioxides  of  the  above  metals, 
sulphates  are  formed  analogous  to  aluminium  sulphate,  and  of 
which  the  composition  is  expressed  by  the  general  formula 
(R2)vi(S04)3.  With  the  sulphates  M2S04,  they  form  alums,  all 
of  which  crystallize  in  regular  octahedra,  and  which  can  be 
mixed  in  one  and  the  same  crystal  without  the  form  of  the 
latter  being  affected  by  the  mixture. 

The  following  are  the  most  important  of  these  compounds: 

Manganese  alum  ....     Mn2(SO*)3.R2SO*  +  24IPO 

Iron  alum Fe2(S04)3.R2SO*  +  24H*0 

Chromium  alum    ....     Cr2(SO*J3.K2SO*   +  24H20 


ALUM.  317 

It  is  seen  that  each  of  these  presents  an  atomic  composition 
similar  to  that  of  ordinary  alum. 


The  aluminium  compounds  are  widely  disseminated  in  nature. 
Feldspar  is  a  double  silicate  of  aluminium  and  potassium.  The 
latter  metal  is  replaced  by  sodium  in  albite,  and  by  calcium  in 
labradorite. 

Many  other  minerals  contain  aluminium  silicate  combined 
with  alkaline  or  earthy  silicates :  such  are  granite,  idiocrase, 
mica,  etc.  The  zeolites  are  silicates  of  aluminium  containing 
water  of  crystallization. 

Clay  is  a  hydrated  silicate  of  aluminium ;  it  results  from  the 
disintegration  of  feldspar  by  the  action  of  water  and  air,  the 
alkaline  silicate  being  gradually  dissolved  and  eliminated.  The 
purest  clay  is  kaolin,  or  porcelain  clay ;  it  contains  alumina, 
silica,  and  water  in  the  proportions  indicated  by  the  formula 
2Si02,AP03,2H20. 

Plastic  clays  are  those  which  form  a  binding  paste  when 
mixed  with  water,  and  acquire  great  hardness  after  being 
baked,  without  fusing.  They  are  used  for  the  manufacture  of 
pottery,  refractory  fire-bricks,  and  crucibles.  Fuller's  earth  is 
a  clay  which  forms  with  water  a  paste  that  is  but  slightly  adhe- 
rent ;  it  is  employed  in  scouring  and  fulling  cloth. 

Marls  are  intimate  mixtures  of  clay  and  chalk;  they  are 
employed  in  agriculture. 

Pottery. — Clay  is  the  basis  of  all  pottery.  Other  matters, 
such  as  sand,  powdered  feldspar  or  quartz,  etc.,  are  generally 
added,  for  while  they  diminish  the  plasticity  of  the  clay,  they 
also  diminish  its  shrinkage  on  baking.  Pottery  is  classified  as 
semi  vitrified  pottery,  such  as  porcelain  and  stoneware ;  porous 
pottery,  such  as  faience  and  bisque;  and  common  pottery  or 
terra-cotta. 

Porcelains. — These  are  manufactured  from  kaolin,  to  which 
sand  is  added  to  prevent  shrinkage,  and  feldspar,  which  causes 
the  ware  to  undergo  a  partial  fusion,  and  renders  it  translucent. 
These  materials  are  finely  pulverized,  mixed  with  water,  and 
the  paste  is  kneaded  for  a  long  time  in  order  to  render  it  homo- 
geneous. Pieces  fashioned  in  this  paste  are  submitted  to  a  pre- 
liminary baking,  which  gives  them  a  certain  degree  of  coherence. 
The  porous  porcelain  thus  obtained  must  be  coated  with  a  var- 
nish which  will  melt  and  spread  upon  its  surface :  this  glaze  is 

27* 


318  ELEMENTS   OF   MODERN   CHEMISTRY. 

formed  of  a  mixture  of  quartz  and  kaolin  reduced  to  an  impal- 
pable powder ;  the  latter  is  suspended  in  water,  into  which  the 
pieces  are  dipped.  They  are  then  subjected  to  a  second  baking 
in  ovens  where  the  temperature  is  sufficiently  elevated  to  fuse 
the  glaze  and  partially  vitrify  the  paste. 

Ceramic  Stonewares. — These  are  manufactured  from  the 
same  materials  as  porcelain,  but  less  pure ;  they  are  therefore 
slightly  colored.  They  are  baked  at  a  high  temperature,  and 
are  glazed  by  throwing  common  salt  upon  the  incandescent 
objects  in  the  furnace ;  hydrochloric  acid  is  disengaged,  and  a 
double  silicate  of  aluminium  and  sodium  is  formed,  which  fuses 
and  spreads  upon  the  surface  of  the  ware. 

Faiences  are  made  from  plastic  clay  mixed  with  quartz  re- 
duced to  an  impalpable  powder.  Articles  formed  of  this  paste 
are  submitted  to  a  preliminary  baking,  and  are  then  coated  with 
a  fusible  glaze,  composed  of  quartz,  potassium  carbonate,  and 
oxide  of  lead.  A  second  baking  causes  the  pieces  to  become 
covered  with  an  impermeable,  vitreous  layer  of  silicate  of  lead 
and  potassium.  This  glaze  is  transparent ;  for  ordinary  ware 
it  is  rendered  opaque  by  the  addition  of  oxide  of  tin.  It  is 
a  true  enamel. 

Common  pottery,  which  serves  for  culinary  purposes,  is  made 
from  ferruginous  clay,  mixed  with  sand  and  marl.  The  glazing 
is  composed  of  a  double  silicate  of  aluminium  and  lead. 


IRON. 

Fe(Ferrum)  =  56 

Natural  State  and  Metallurgy. — Iron  is  the  most  impor- 
tant of  the  metals.  Its  preparation  and  working  are  difficult, 
therefore  it  was  not  the  first  metal  used  by  civilized  man.  The 
bronze  age  preceded  the  iron  age,  and  those  who  first  employed 
the  latter  metal  probably  extracted  it  from  the  masses  which 
fall  from  time  to  time  upon  the  surface  of  the  earth,  and  are 
known  as  meteorites.  Their  principal  constituent  is  metallic 
iron,  which  is  alloyed  with  nickel,  cobalt,  and  chromium. 

Iron  is  employed  in  three  principal  forms  :  soft  or  malleable 
iron,  cast  iron,  and  steel.  Soft  iron  is  almost  pure  iron ;  cast 
iron  is  a  combination  of  iron  with  carbon  and  silicon ;  steel 
also  contains  carbon,  but  in  smaller  proportion  than  cast  iron. 

The  principal  ores  of  iron  are  the  magnetic,  or  black  oxide, 


IRON. 


319 


Fe304,  red  hematite,  Fe203,  and  spathic  iron  or  ferrous  carbon- 
ate, FeCO3.  The  various  hydrates  of  the  sesquioxide  (oolitic 
iron,  broivn  hematite,  etc.)  and  ferrous  carbonate  mixed  with 
clay  (bog-iron  ore),  are  more  abundant  than  the  preceding,  but 
are  not  as  rich  and  are  less  valuable. 

All  of  these  minerals  are  oxidized.  If  the  ore  contain  sul- 
phur, that  element  is  first  driven  out  by  roasting.  The  metal- 
lurgy of  iron  then  consists  in  reducing  the  oxide  with  carbon, 
and  separating  the  reduced  iron  from  the  earthy  matter,  which 
is  generally  silicious.  Two  methods  are  employed  for  this 
purpose.  The  first  consists  in  heating  the  rich  ores  with 
charcoal  alone  ;  part  of  the  oxide  of  iron  then  combines  with 
the  gangue,  forming  a  very  fusible  slag  (double  silicate  of 
aluminium  and  iron).  This  is  the  Catalan  method.  The 
other  consists  in  mixing  the  ore  with  coal  and  calcium  carbon- 
ate ;  the  gangue  then  com- 
bines with  the  lime,  forming 
a  double  silicate  of  lime  and 
aluminium,  which  fuses  only 
at  a  very  high  temperature. 
Under  these  conditions  the 
iron  unites  with  a  portion 
of  the  carbon,  forming  cast 
iron.  This  is  the  blast-fur- 
nace method. 

Catalan  Method. — This  is 
only  applicable  to  very  rich 
ores  and  in  countries  where 
combustibles  are  expensive, 
as  in  Spain,  the  Pyrenees, 
and  in  Corsica. 

Fig.  102  represents  a  sec- 
tion of  a  Catalan  furnace  ;  it 
is  a  trough-shaped  masonry 

furnace  with  a  hearth.     The  FIG.  102. 

materials  are  placed  in  two 

piles,  side  by  side,  upon  a  layer  of  well-ignited  charcoal ;  one  pile 
consists  of  charcoal  and  is  next  the  tuyere ;  the  other  is  the 
ore,  equal  to  half  the  quantity  of  charcoal,  and  is  placed  oppo- 
site. The  combustion  is  sustained  by  the  blast  from  a  tuyere, 
D,  which  reaches  the  border  of  the  hearth.  The  carbon 
dioxide  here  formed  is  converted  into  carbon  monoxide  by  the 


320 


ELEMENTS    OF    MODERN    CHEMISTRY. 


mass  of  incandescent  charcoal,  and  the  latter  gas  reduces  the 
ore,  again  passing  into  the  state  of  dioxide.  Metallic  iron  is 
thus  formed,  and  at  the  same  time  a  portion  of  the  ferric 
oxide  is  reduced  to  ferrous  oxide,  and  combines  with  the 
gangue,  forming  a  double,  alumino-ferrous  silicate,  which  is  very 
fusible  and  constitutes  the  slag.  The  reduced  iron  collects  in 
the  bottom  of  the  hearth  in  the  form  of  a  spongy  mass,  which 
is  agglutinated  and  forged  under  the  hammer. 


FIG.  103. 


Blast-furnace  Process. — All  iron  ores  may  be  treated  by  this 
method.  They  are  crushed  and  introduced  with  alternate 
layers  of  limestone  and  coal  into  the  blast-furnace  (Fig.  103). 
The  latter  has  the  form  of  two  cones,  the  bases  of  which  are 


IRON.  321 

joined  together.  It  is  closed  at  the  bottom,  and  hot  air  is  in- 
jected through  tuyeres  to  sustain  the  combustion.  It  is  open  at 
the  top,  where  it  is  continually  charged  with  fresh  materials,  as 
the  incandescent  mass  sinks  in  the  furnace  and  the  molten  mate- 
rials are  drawn  off  below.  The  latter  first  collect  in  a  cavity 
placed  below  the  vent  of  the  tuyere,  and  separate  on  this 
hearth  into  metal,  which  sinks  to  the  bottom,  and  slag,  which 
floats  and  flows  over  the  edge.  When  the  crucible  is  full  of 
molten  metal,  the  latter  is  run  off  into  channels  made  in  sand 
upon  the  floor  of  the  casting-room.  In  these  rough  moulds  it 
solidifies  in  bars  having  a  semicircular  section,  which  are  called 
pigs. 

The  reactions  which  take  place  in  the  blast-furnace  are  of 
great  interest.  At  the  lower  part,  where  the  temperature  is 
the  highest,  carbon  dioxide  is  produced  by  the  combustion  of 
the  coal ;  farther  up,  in  the  widest  portion,  this  gas  is  reduced 
to  carbon  monoxide  by  the  incandescent  coal ;  still  higher, 
where  the  furnace  begins  again  to  contract,  and  where  the 
temperature  is  dull  red,  the  carbon  monoxide  reduces  the  oxide 
of  iron,  and  a  spongy  mass  of  metallic  iron  is  there  formed. 

In  descending,  this  iron  unites  with  part  of  the  carbon,  and 
at  the  same  time  the  silica  of  the  gangue  combines  with  the 
lime,  forming  a  silicate  which  fuses  and  constitutes  the  slag. 

A  small  quantity  of  silica  is  reduced  in  the  hottest  part  of 
the  furnace,  and  the  silicon  formed  combines  with  the  cast  iron. 

Cast  iron  is  converted  into  soft  iron  by  refining ;  this  opera- 
tion consists  in  removing  from  the  cast  iron  the  greater  part 
of  its  carbon.  For  this  purpose  it  is  melted  in  contact  with 
the  air ;  the  carbon,  silicon,  and  a  small  proportion  of  iron  are 
oxidized,  forming  a  basic  silicate,  of  which  the  excess  of  oxide 
is  finally  reduced  by  the  carbon  of  the  cast  iron.  The  latter 
thus  becomes  less  fusible,  and  is  converted  into  a  spongy  mass 
of  soft  iron.  Several  of  these  masses  are  united  and  the  scoriae 
expressed  from  them  by  the  blows  of  a  steam-hammer.  Or  the 
metal  is  melted  on  the  hearth  of  a  reverberatory  furnace  under 
a  layer  of  ferruginous  scoriae  and  scales  of  oxide  of  iron ;  the 
oxygen  of  these  materials  burns  the  carbon  out  of  the  cast  iron, 
the  whole  mass  being  vigorously  stirred.  The  latter  operation 
is  called  puddling. 

Preparation  of  Pure  Iron. — Pure  iron  may  be  obtained  by 
reducing  ferric  oxide  by  hydrogen  at  a  temperature  near  red- 
ness, or  by  passing  hydrogen  over  anhydrous  ferrous  chloride ' 
o* 


322  ELEMENTS   OF   MODERN   CHEMISTRY. 

contained  in  an  incandescent  porcelain  tube.  Hydrochloric 
acid  is  formed  and  evolved,  and  the  iron  remains  as  a  gray, 
spongy  mass,  having  a  metallic  lustre  where  it  has  been  in 
contact  with  the  porcelain  (Peligot). 

Properties  of  Soft  Iron. — Forged,  or  bar  iron,  is  not  chem- 
ically pure.  It  contains  a  small  quantity  of  carbon,  and  traces 
of  silicon,  sulphur,  and  phosphorus,  and  even  nitrogen.  The 
purest  soft  iron  is  that  used  for  the  teeth  of  carding-inachines 
and  for  piano-strings. 

The  density  of  forged  iron  varies  from  7.4  to  7.9.  It  is 
very  tenacious,  ductile,  and  malleable.  When  rolled  out,  it  is 
called  sheet  iron.  Tin  plate  is  sheet  iron  covered  with  a  layer 
of  tin.  Galvanized  iron  is  coated  with  a  surface  of  zinc. 

Iron  melts  only  at  the  highest  heats  of  a  wind-furnace. 
When  softened  by  a  white  heat,  it  may  be  soldered  to  itself,  or 
welded,  a  very  important  property  for  the  working  of  the  metal. 

Iron  is  attracted  by  the  magnet ;  it  is  magnetic ;  but  it  is 
not,  like  steel,  capable  of  retaining  magnetism  when  removed 
from  the  magnetic  influence. 

It  is  not  altered  by  dry  air  at  ordinary  temperatures,  but  at 
a  red  heat  it  absorbs  oxygen  and  is  converted  into  scales  of 
black  oxide  of  iron. 

Iron  may  be  obtained  as  an  impalpable  powder  by  reducing 
finely-divided  ferric  oxide  by  a  current  of  hydrogen  at  as  low  a 
temperature  as  possible.  In  this  state  it  takes  fire  when  ex- 
posed to  the  air  at  ordinary  temperatures :  it  is  pyrophoric. 

Iron  rapidly  becomes  oxidized  in  moist  air ;  it  becomes  cov- 
ered with  a  layer  of  rust,  which  is  ferric  hydrate.  It  is  con- 
sidered that  the  oxidation  of  iron  moistened  with  water  is  first 
set  up  by  the  oxygen  dissolved  in  the  water;  it  continues 
with  greater  energy  as  soon  as  a  light  coat  of  ferric  hydrate 
has  been  formed  on  the  metal.  The  hydrate  forms  a  voltaic 
couple  with  the  iron  itself,  by  which  the  water  is  decomposed ; 
part  of  the  hydrogen  displaced  by  the  iron  combines  with  the 
nitrogen  of  the  air,  forming  ammonia;  indeed,  rust  always 
contains  a  small  proportion  of  ammonia. 

Iron  decomposes  water  at  a  red  heat,  setting  free  the  hydro- 
gen. It  dissolves  readily  in  hydrochloric  acid,  liberating  impure 
and  fetid  hydrogen.  Its  oxidation  by  nitric  acid  is  attended 
by  curious  phenomena. 

If  dilute  nitric  acid  be  poured  upon  iron  tacks,  the  metal  is 
at  once  attacked  with  an  abundant  disengagement  of  red  vapors. 


IRON.  323 

On  the  other  hand,  the  same  metal  is  not  attacked  by  very 
concentrated  nitric  acid  (monohydrated),  and  after  having  been 
exposed  to  the  strong  acid,  the  tacks  may  be  put  into  dilute  acid, 
and  the  latter  will  then  be  found  to  have  no  effect. 

By  the  action  of  the  concentrated  acid,  the  iron  becomes 
passive;  its  surface  is  covered  with  a  thin  layer  of  gas  which 
protects  it.  But  if  it  be  touched  at  any  point  with  a  copper 
wire  while  in  the  dilute  acid,  chemical  action  will  instantly  be 
re-established. 

Cast  Iron  and  Steel. — The  properties  and  appearance  of  cast 
iron  differ  with  the  proportions  of  carbon  and  silicon  which  it 
contains.  The  iron  does  not  form  definite  compounds  with 
these  bodies;  they  seem  to  be  dissolved  by  the  cast  iron  when 
it  is  liquid.  When  cast  iron  containing  much  carbon  is  quickly 
cooled,  it  becomes  hard,  brittle,  whiter  than  soft  iron,  and  seems 
homogeneous.  This  is  white  iron.  When  slowly  cooled,  a  large 
proportion  of  the  carbon  is  deposited  as  laminae  of  graphite, 
and  the  less  homogeneous  iron  then  possesses  a  certain  degree 
of  malleability  :  it  is  gray  iron. 

Some  cast  irons  contain  traces  of  sulphur  and  phosphorus; 
they  remain  white  even  after  very  slow  cooling.  Others  are 
lamellar  and  glittering;  they  contain  manganese  and  are  rich 
in  carbon. 

The  proportion  of  carbon  contained  in  cast  iron  varies  from 
2  to  5.5  per  cent.  Steel  contains  less  carbon,  from  0.7  to  2 
per  cent.  The  quantities  of  carbon  contained  in  steel  and  even 
in  cast  iron  render  it  difficult  to  suppose  that  these  products 
are  veritable  carbides  of  iron. 

Steel  may  be  obtained  by  a  partial  decarbonization  of  cast 
iron.  Manganiferous  iron  is  especially  applicable  for  this  prep- 
aration. It  is  submitted  to  a  partial  refining,  being  maintained 
in  the  liquid  state  for  some  hours  under  a  layer  of  scoriae  rich 
in  oxide  of  iron.  A  part  of  the  carbon  is  burned  out  by  the 
oxygen  of  this  oxide  :  natural  steel  is  thus  obtained. 

Soft  iron  may  be  converted  into  steel.  The  operation  is  con- 
ducted in  cases  of  refractory  fire-clay,  into  which  bars  of  iron, 
and  charcoal-powder,  mixed  with  a  small  quantity  of  ashes  and 
common  salt,  are  introduced  in  alternate  layers.  The  bars  being 
thus  isolated  in  a  bed  of  charcoal,  the  cases  are  closed  and 
heated  to  redness  in  a  furnace.  The  incandescent  metal  absorbs 
carbon,  and  at  the  termination  of  the  operation  is  found  con- 
verted into  steel  by  cementation. 


324  ELEMENTS   OF   MODERN   CHEMISTRY. 

The  most  homogeneous  and  most  valuable  steel  is  cast  steel. 
It  is  obtained  by  fusing  crude  steel  in  crucibles  in  a  wind-fur- 
nace. 

Bessemer  has  introduced  an  important  improvement  in  the 
manufacture  of  steel.  His  process,  which  bears  his  name,  con- 
sists in  adding  variable  quantities  of  a  properly-constituted  cast 
iron  to  molten  and  perfectly  refined  soft  iron. 

In  this  process,  the  iron  to  be  converted  into  steel  is  decar- 
bonized by  a  current  of  air  which  is  forced  through  the  molten 

metal  by  strong  press- 
ure. The  operation  is 
conducted  in  an  appa- 
ratus represented  in 
Fig.  104,  which  is 
called  the  converter.  It 
has  an  ovoid  form,  is 
constructed  of  strong 
plate  iron,  and  is  well- 
lined  with  refractory 
fire-bricks.  It  is  ar- 
ranged on  trunnions,  so 
that  an  oscillating  move- 
ment may  be  given  to  it. 
The  air  arrives  under 
pressure  by  the  tuyeres 
which  open  into  the  bot- 
tom of  the  converter. 

T?16  latter  is  first  filled 
with  incandescent  coke, 

which  is  brought  into  active  combustion  by  the  blast.  When 
the  interior  of  the  converter  is  heated  to  whiteness,  the  coke 
is  emptied  out  and  replaced  by  the  molten  cast  iron,  the  con- 
verter being  inclined  to  prevent  the  entrance  of  the  metal  into 
the  tuyeres.  The  blast  is  then  again  turned  on,  and  the  com- 
pressed air  bubbling  through  the  molten  metal  burns  out  all 
of  the  carbon.  A  flame  of  great  brilliancy  rushes  from  the 
orifice  of  the  apparatus,  and  the  aspect  of  this  flame  indicates 
precisely  the  progress  of  the  operation  and  its  termination. 
At  this  moment  the  apparatus  is  inclined,  the  blast  arrested, 
and  a  sufficient  quantity  of  melted  cast  iron  or  spiegeleisen,  a 
crystalline  cast  iron  rich  in  carbon,  is  added  to  the  now  refined 
iron  to  convert  the  whole  into  steel ;  about  7  per  cent,  of  spie- 


OXIDES   OF   IRON.  325 

geleisen  is  required.  The  steel  is  then  run  out  into  suitable 
moulds. 

The  valuable  qualities  of  steel  are  well  known.  It  is  suscep- 
tible of  a  high  polish ;  it  is  ductile  and  malleable  like  iron,  and 
can  also  be  forged.  At  the  temperature  at  which  malleable 
iron  becomes  soft,  steel  melts.  It  becomes  hard  and  brittle 
when  it  is  suddenly  cooled  after  having  been  heated  to  redness. 
This  operation,  which  is  called  tempering,  develops  new  quali- 
ties in  the  steel, — elasticity  and  hardness.  It  assumes  these 
properties  in  different  degrees,  according  to  the  rapidity  of  the 
cooling,  and  the  difference  between  the  temperature  to  which 
it  has  been  heated  and  that  to  which  it  is  cooled.  The  greater 
this  difference,  and  the  more  rapid  the  cooling,  the  harder  will 
the  steel  become.  After  a  slow  cooling,  it  is  soft  and  mallea- 
ble like  iron. 

When  tempered  steel  is  heated,  and  allowed  to  cool  slowly, 
it  partly  or  entirely  loses  its  hardness.  It  loses  it  entirely  if 
it  be  heated  to  the  temperature  to  which  it  was  exposed  before 
tempering.  Its  temper  is  drawn  incompletely,  that  is,  it  re- 
tains a  certain  amount  of  hardness  and  elasticity,  if  it  be  re- 
heated to  inferior  temperatures.  The  qualities  which  it  will 
assume  after  cooling  may  be  predicted  from  the  various  tints 
developed  on  its  surface  during  the  heating.  Each  of  these 
tints  corresponds  to  a  determined  temperature. 

Straw-yellow  corresponds  to  220° 
Brown  "  255° 

Light  blue  "  285-290° 

Jn.ligo-blue  "  295° 

Sea-green  "  331° 

OXIDES   OF  IRON. 

Three  oxides  of  iron  are  known : 

Ferrous  oxide FeO 

Ferric  oxide Fe2O3 

Ferroso-ferric  oxide .  Fe3O4 

Fremy  has  also  discovered  the  existence  of  a  ferric  acid,  of 
which  the  composition  is  not  certainly  established. 

Ferrous  Oxide,  FeO. — Debray  has  obtained  this  oxide  by 
partially  reducing  ferric  oxide.  The  latter  is  heated  in  a  cur- 
rent of  gas  formed  of  equal  volumes  of  carbon  monoxide  and 
carbon  dioxide.  A  black  powder  remains,  which  is  ferrous 
oxide. 

Fe203  +  CO  =  2FeO  -f  CO2 
28 


326  ELEMENTS    OF    MODERN    CHEMISTRY. 

Ferric  Oxide,  Fe203. — This  is  found  anhydrous  in  nature 
in  red  hematite  and  specular  iron.  It  may  be  prepared  by 
calcining  ferrous  sulphate,  or  green  vitriol.  This  salt  first 
loses  its  water,  and  then  at  a  red  heat  decomposes  into  sul- 
phuric anhydride,  sulphurous  oxide,  and  ferric  oxide. 

2FeS04  =  SO3  +  SO2  +  Fe203 

A  red  powder  is  thus  obtained,  which  is  known  as  colcothar, 
or  jeweller's  rouge. 

This  oxide  is  amorphous,  while  red  hematite  is  crystallized  in 
acute  rhombohedra.  H.  Deville  has  succeeded  in  converting 
the  amorphous  oxide  into  the  crystallized  by  heating  the  former 
to  redness  in  a  very  slow  current  of  hydrochloric  acid. 

Rust  is  ferric  hydrate,  a  combination  of  ferric  oxide  with 
water,  and  ordinarily  presents  the  composition 

2Fe203  -f  3H20 

Such  a  hydrate  is  also  encountered  in  nature  as  brown 
hematite.  Another  natural  hydrate,  containing  Fe203  -j-  IPO, 
is  known  under  the  name  of  gcethite. 

Ammonia  or  potassium  hydrate  will  at  once  produce  a  volu- 
minous and  flocculent,  rust-colored  precipitate  in  a  solution  of 
ferric  chloride.  This  precipitate  constitutes  a  ferric  hydrate. 

But  if  an  excess  of  tartaric  acid  be  added  to  the  solution  of 
a  ferric  salt,  the  liquid  may  be  saturated  with  potassium  hy- 
drate and  will  still  remain  clear,  no  precipitate  of  ferric  hydrate 
being  formed. 

Advantage  is  taken  of  this  property  in  analysis  for  the  sepa- 
ration of  ferric  oxide  from  other  oxides  which  tartaric  acid  does 
not  retain  in  solution  in  an  alkaline  liquid. 

If  a  solution  of  ferric  acetate  be  poured  into  a  dialyser 
(page  199),  and  the  water  in  the  exterior  vessel  be  frequently 
changed,  the  salt  will  finally  be  entirely  decomposed.  Acetic 
acid  will  pass  through  the  membrane,  while  ferric  hydrate  will 
remain  dissolved  in  the  water  in  the  dialyser  (Graham). 

Ferroso-ferric  Oxide,  Fe304. — This  compound,  also  called 
magnetic  oxide  of  iron,  constitutes  the  black  scales  which  form 
upon  the  surface  of  iron  when  it  is  heated  to  redness  in  the 
air ;  it  may  be  regarded  as  a  compound  of  ferrous  and  ferric 
oxides.  FeO  Fe203  =  Fe304. 


SULPHIDES  OF  IRON — CHLORIDES  OP  IRON.     327 


SULPHIDES   OF   IRON. 

Several  sulphides  of  iron  are  known. 

The  disulphide,  or  pyrites,  FeS2,  a  largely-diffused  mineral, 
is  the  most  important  of  these  sulphides.  It  occurs  in  two 
distinct  forms : 

Yellow  pyrites,  which  crystallizes  in  cubes.  It  occurs  as 
brilliant  cubes,  or  dodecahedra,  having  a  yellow  color  and  a 
metallic  lustre. 

White  pyrites,  which  forms  rhombic  prisms,  variously  modi- 
fied, and  presents  a  dull,  greenish-yellow  color.  This  variety 
is  much  more  alterable  than  the  other,  and  possesses  a  great 
tendency  to  attract  oxygen  from  the  air  and  become  converted 
into  sulphate.  When  heated  in  closed  vessels,  pyrites  loses  a 
part  of  its  sulphur. 

A  combination  of  monosulphide  and  sesquisulphide  of  iron 
is  encountered  in  nature ;  it  crystallizes  in  regular  hexagonal 
prisms  and  is  called  magnetic  pyrites. 

Monosulphide  of  Iron,  FeS,  is  found  in  small  quantity  in 
many  meteorites.  It  is  ordinarily  obtained  by  heating  to  red- 
ness in  a  covered  crucible  a  mixture  of  three  parts  of  iron- 
filings  and  two  parts  of  sulphur.  When  the  mixture  has 
fused,  it  is  poured  out  and  solidifies  to  a  brittle,  blackish  mass, 
having  a  metallic  reflection.  In  this  state,  it  is  used  for  the 
preparation  of  hydrogen  sulphide. 


CHLORIDES   OF  IRON. 

Ferrous  Chloride,  Fed2,  is  obtained  anhydrous  by  the  action 
of  dry  hydrochloric  acid  gas  upon  metallic  iron.  It  forms  white 
pearly  scales.  When  iron  is  treated  with  aqueous  hydrochloric 
acid,  it  dissolves,  and  hydrogen  is  disengaged.  The  green, 
filtered  liquid  deposits,  when  sufficiently  concentrated,  bluish- 
green,  oblique  rhombic  prisms.  This  is  hydrated  ferrous  chlo- 
ride, Fed2  -f  4H2O. 

Ferric  Chloride,  Fe2Cl6,  is  formed  when  a  current  of  chlorine 
is  passed  over  iron-turnings  heated  in  a  glass  or  porcelain  tube. 
The  two  bodies  combine  with  incandescence,  and  if  the  chlorine 
be  in  excess,  ferric  chloride  will  be  obtained  as  a  brilliant  black, 
crystalline  sublimate. 


328  ELEMENTS    OF    MODERN   CHEMISTRY. 

This  body  is  very  soluble  in  water  and  forms  a  yellow-brown 
solution.  The  latter  may  be  obtained  by  dissolving  ferric  oxide, 
such  as  powdered  hematite,  in  hot  hydrochloric  acid,  or  by 
passing  chlorine  into  a  solution  of  ferrous  chloride.  Ferric 
chloride  is  also  soluble  in  alcohol. 

FERROUS   SULPHATE. 

7H2O 


This  salt  has  long  been  known  under  the  names  green 
vitriol  and  copperas.  It  is  obtained  by  exposing  iron  pyrites 
to  the  air,  or  roasting  that  mineral  at  a  moderate  heat.  It  is 
generally  prepared  by  dissolving  iron  in  dilute  sulphuric  acid, 
and  it  is  a  residue  from  the  preparation  of  hydrogen  sulphide 
by  means  of  iron  sulphide  and  dilute  sulphuric  acid. 

It  crystallizes  in  oblique  rhombic  prisms,  containing  7  mol- 
ecules of  water  of  crystallization.  When  exposed  to  the  air, 
these  crystals  effloresce  slightly,  and  at  the  same  time  their 
surface  becomes  yellow  from  absorption  of  oxygen  and  the 
formation  of  ferric  subsulphate. 

2FeS04  +  0  =  Fe20(SO)2  =  Fe203.2S03 

When  heated,  they  lose  their  water,  of  which  six  molecules 
are  disengaged  at  114°,  and  the  seventh  only  at  300°.     At  a 
higher  temperature  the  salt  decomposes  into  sulphurous  oxide, 
and  a  ferric  subsulphate  different  from  the  preceding. 
2FeSO  ==  SO2  +  (Fe2O2)SO* 

The  crystals  of  ferrous  sulphate  are  freely  soluble  in  water. 
100  parts  of  the  salt  dissolve  in  164  parts  of  water  at  10°,  and 
in  30  parts  of  boiling  water.  The  green  solution  absorbs  oxy- 
gen from  the  air,  becomes  troubled,  and  deposits  yellow  ferric 
subsulphate. 

Other  hydrates  of  ferrous  sulphate  are  known.  According 
to  Mitscherlich,  a  saturated  boiling  solution  of  the  salt  deposits 
at  80°  crystals  containing  four  molecules  of  water.  According 
to  Marignac,  when  a  solution  of  ferrous  sulphate  containing 
free  sulphuric  acid  is  evaporated  in  a  vacuum,  crystals  are  first 
deposited  which  contain  7  molecules  of  water,  then  a  sulphate 
FeSO4  -f  5H20,  and  finally,  FeSO4  +  4H20. 

The  sulphate  FeSO4  -f-  5H20,  is  isomorphous  with  crystal- 
lized cupric  sulphate  (blue  vitriol),  and  like  it  crystallizes  in 
dissymetric  prisms. 


FERRIC  SULPHATE — FERROUS  CARBONATE.      329 

FERRIC   SULPHATE. 

Fe2(SO)3 

This  salt  is  obtained  by  heating  ferrous  sulphate  with  nitric 
and  sulphuric  acids ;  the  brown  solution  is  evaporated,  and  the 
residue  well  dried. 

2FeS04  -f  H2S04  -f  0  =  H20  +  Fe2(S04)3 

Ferric  sulphate  is  a  slightly -yellowish,  white  mass,  which 
dissolves  completely,  but  very  slowly,  in  water.  The  solution 
is  yellow-brown,  and  has  an  acid  reaction. 

When  concentrated  by  evaporation,  it  deposits  a  deliquescent, 
yellowish,  crystalline  mass,  which  constitutes  hydrated  ferric 
sulphate. 

There  are  several  ferric  subsulphates  ;  those  which  have 
been  mentioned  above  result  from  the  action  of  one  molecule 
of  ferric  oxide  upon  one  or  two  molecules  of  sulphuric  acid, 
the  neutral  sulphate  resulting  from  the  action  of  one  molecule 
of  ferric  oxide  upon  three  molecules  of  sulphuric  acid. 

IFSO4  4-  Fe203  =  H20  +  (Fe202)"SO4 

Ferric  monosulphate. 


Ferric  disulphate. 

H2S04  (  SO4 

H2SO4  +  Fe203  =  3H20  +          (Fe2/1  3  SO4 
H'SO*  (  SO4 

Ferric  trisnlphate  (normal  sulphate). 


FERROUS  CARBONATE. 

FeCO3 

Spathic  iron  ore,  which  crystallizes  in  rhombohedra,  is  fer- 
rous carbonate.  When  a  solution  of  sodium  carbonate  is  added 
to  a  solution  of  ferrous  sulphate,  a  greenish-white  precipitate 
is  obtained,  which  rapidly  becomes  colored  in  the  air,  absorb- 
ing oxygen  and  losing  carbonic  acid.  When  recently  precipi- 
tated, it  dissolves  in  a  large  excess  of  carbonic  acid. 

Characters  of  Ferrous  Salts.  —  The  solutions  of  these  salts 
are  green  j  they  are  not  precipitated  by  hydrogen  sulphide,  but 
ammonium  sulphide  forms  a  black  precipitate  of  ferrous  sul- 

28* 


330  ELEMENTS   OF   MODERN   CHEMISTRY. 

phide.  Potassium  hydrate  or  ammonia  produces  a  greenish- 
white  precipitate  of  ferrous  hydrate,  insoluble  in  an  excess  of 
the  reagent,  and  rapidly  becoming  colored  in  the  air.  Potas- 
sium ferrocyanide  (yellow  prussiate  of  potash)  forms  with  fer- 
rous salts  a  light-blue  precipitate.  Potassium  ferricyanide  (red 
prussiate)  forms  a  dark-blue  precipitate.  Solution  of  gall-nuts 
does  not  color  ferrous  salts. 

Characters  of  Ferric  Salts. — Hydrogen  sulphide  produces 
a  precipitate  of  sulphur,  reducing  the  salts  to  the  ferrous  state. 
Ammonium  sulphide  precipitates  them  black.  Potassium  hy- 
drate and  ammonia  form  red-brown  precipitates  of  ferric  hy- 
drate, insoluble  in  an  excess  of  the  reagent.  Potassium  ferro- 
cyanide forms  a  dark-blue  precipitate  which  is  Prussian  blue. 

Potassium  ferricyanide  produces  a  dark-brown  color  without 
precipitation.  Potassium  sulphocyanate  gives  a  blood-red  color. 

Solution  of  gall-nuts  forms  a  bluish-black  precipitate  which 
constitutes  ink. 

ZINC. 

Zn  =  65.2 

Treatment  of  Zinc  Ores. — The  zinc  ores  which  are  worked 
are  calamine  and  blende.  Calamine  is  carbonate  of  zinc,  often 
mixed  with  silicate ;  it  contains  also  oxide  of  iron.  Blende  is 
sulphide  of  zinc;  it  frequently  contains  a  small  quantity  of 
ferrous  sulphide,  which  gives  it  a  brown  color,  more  or  less 
intense. 

Zinc  ores  are  abundant  in  England,  Silesia,  Belgium,  and 
throughout  the  United  States.  They  are  generally  accom- 
panied by  other  minerals;  thus,  blende  is  often  mixed  with 
pyrites  and  galena  (lead  sulphide).  The  ore  is  then  first  sub- 
mitted to  an  ingenious  system  of  washing,  by  which  the  various 
sulphides  separate  from  each  other  by  reason  of  their  different 
densities. 

In  order  to  extract  the  zinc  from  blende  separated  by  this 
method,  or  from  calamine,  the  minerals  are  first  roasted.  By 
the  action  of  heat  calamine  loses  carbonic  acid  gas  and  water, 
and  the  blende  disengages  sulphurous  oxide  and  is  converted 
into  zinc  oxide.  Thus  converted  into  oxide,  and  rendered  more 
friable  by  the  heat,  the  zinc  ores  are  pulverized  and  calcined 
with  charcoal.  Carbon  monoxide  is  disengaged,  and  the  zinc 
set  at  liberty  volatilizes,  and  is  condensed  in  suitable  recipients. 


ZINC. 


331 


The  operation  is  conducted  in  cylinders  of  refractory  clay,  a 
number  of  which  are  arranged  in  a  furnace,  and  their  open 
extremities  connected  with  conical  recipients  of  galvanized  iron 
(Fig.  105).  In  Silesia,  these  cylindrical  retorts  are  replaced  by 
muffles,  which  are  heated  in  a  furnace  and  communicate  with 
recipients  placed  outside  (Fig.  106). 


FIG.  105. 


FIG.  106. 


In  England,  the  reduction  of  the  roasted  ore  is  accomplished 
in  crucibles,  through  the  bottoms  of  which  pass  vertical  tubes 
which  terminate  in  a  reservoir  below  the  furnace.  The  zinc 
vapors  first  rise  and  then  descend  by 
the  tube,  and  as  they  condense,  the 
melted  metal  flows  into  the  recipient. 
The  operation  is  called  distillation  per 
descensum  (Fig.  107). 

The  zinc  of  commerce  is  not  always 
pure,  especially  when  it  occurs  in 
masses ;  it  contains  small  quantities  of 
iron,  copper,  lead,  cadmium,  carbon, 
and  arsenic.  Sheet  zinc  is  generally 
less  impure.  Zinc  may  be  purified 
by  melting  it  several  times  with  small 
quantities  of  nitre. 

Properties. — Zinc   has    a  bluish-, 
white  color;  its  density  varies  from  6.86  to  7.2,  according  as 


FIG.  107. 


332  ELEMENTS   OF   MODERN   CHEMISTRY. 

it  has  been  melted  or  rolled ;  its  fracture  is  laminated  and  bril- 
liant. Commercial  zinc  is  brittle  at  ordinary  temperatures  ;  it 
becomes  malleable  at  a  few  degrees  above  0°,  but  when  heated 
to  200°  it  again  becomes  brittle.  It  melts  at  410°,  and  distils 
at  about  1000°  (H.  Deville  and  Troost).  Its  surface  soon 
tarnishes  in  moist  air,  but  the  oxidation  is  only  superficial. 
It  is  due  to  the  formation  of  a  hydrocarbonate  of  zinc,  which 
covers  the  metal  with  an  impermeable  surface  and  protects  it 
from  further  oxidation. 

When  heated  to  redness  in  contact  with  the  air,  zinc  vola- 
tilizes and  burns  with  a  greenish  flame,  being  converted  into 
oxide,  which  rises  as  smoke  and  falls  in  very  light,  white  flakes, 
formerly  called  flowers  of  zinc  or  philosopher's  wool. 

Zinc  dissolves  with  evolution  of  hydrogen  in  hydrochloric 
and  sulphuric  acids,  and  in  boiling  solutions  of  potassium  and 
sodium  hydrates.  When  perfectly  pure,  it  is  dissolved  with 
difficulty  by  dilute  sulphuric  acid  at  ordinary  temperatures,  and 
the  easy  solubility  of  the  metal  of  commerce  must  be  attrib- 
uted to  the  presence  of  small  quantities  of  foreign  metals.  The 
latter  being  electro-negative  in  contact  with  zinc,  form  voltaic 
couples,  in  which  the  zinc  is  the  more  oxidizable  metal. 

Galvanized  iron  is  iron  covered  with  a  thin  layer  of  zinc;  it 
is  prepared  by  plunging  carefully-cleaned  iron  objects  into  a 
bath  of  molten  zinc. 

Brass  is  an  alloy  of  copper  and  zinc,  obtained  by  melting  the 
two  metals  together  in  crucibles. 

ZINC   OXIDE. 
ZnO 

This  oxide  is  prepared  in  the  arts  by  heating  zinc  in  large 
muffles ;  the  product  is  separated  from  traces  of  metallic  zinc 
by  suspending  it  in  water  and  rapidly  decanting  the  white 
liquid.  The  zinc  sinks  to  the  bottom  of  the  vessel  before  the 
lighter  white  powder  has  time  to  deposit ;  the  latter  is  therefore 
carried  by  the  water  into  a  second  vessel,  where  it  is  allowed 
to  settle.  The  process  is  called  elutriation. 

Oxide  of  zinc  is  white  ;  it  is  irreducible  by  heat  and  is  insolu- 
ble in  water.  A  hydrate  of  this  oxide  is  precipitated  when  an 
alkali  is  added  to  the  solution  of  a  zinc  salt. 

ZnSO4     +     2KOH     =     K2S04     -f     Zn(OH)2 

Ziuc  sulphate.  Zinc  hydrate. 


ZINC   SULPHIDE — ZINC   CHLORIDE.  333 

An  excess  of  alkali  will  redissolve  the  precipitate. 
Zinc  oxide  is  largely  used  in  the  arts  as  a  substitute  for 
white  lead  as  a  pigment. 

ZINC   SULPHIDE. 

ZnS 

The  blende  which  occurs  in  nature  is  sulphide  of  zinc.  It 
crystallizes  generally  in  regular  octahedra,  sometimes  in  double 
pyramids  of  six  faces  (Friedel). 

On  adding  an  alkaline  sulphide  to  a  neutral  solution  of  a 
zinc  salt  a  white  precipitate  is  obtained,  which  is  hydrated  zinc 
sulphide. 

When  moderately  heated  in  contact  with  the  air,  zinc  sul- 
phide absorbs  four  atoms  of  oxygen  and  is  converted  into  sul- 
phate. At  a  very  high  temperature  it  is  converted  into  oxide, 
with  formation  of  sulphurous  oxide. 

ZINC   CHLORIDE. 

ZnCl2 

Zinc  reduced  to  thin  sheets  will  burn  in  chlorine.  Zinc 
chloride  is  prepared  in  the  laboratory  by  dissolving  zinc  in 
hydrochloric  acid.  The  aqueous  solution,  evaporated  to  a 
syrupy  consistence,  deposits  a  hydrated  chloride,  ZnCl2  -f-  H20, 
crystallizing  in  deliquescent  octahedra.  This  salt  loses  its 
water  when  strongly  heated,  and  melts  at  about  250°.  On 
cooling,  a  solid  white  mass  is  obtained,  which  is  the  anhydrous 
chloride  ;  in  this  state  it  is  very  avid  of  water  and  deliquesces 
when  exposed  to  the  air.  It  volatilizes  without  decomposition 
at  a  red  heat.  It  is  very  soluble  in  water,  and  dissolves  also 
in  alcohol. 

ZINC  SULPHATE. 

ZnSO4  +  7H2O 

This  salt  was  formerly  known  as  white  vitriol.  It  is  ob- 
tained by  moderately  roasting  blende.  The  latter  being  often 
mixed  with  pyrites,  zinc  sulphate  and  ferrous  sulphate  are 
formed,  and  when  the  product  of  the  roasting  is  lixiviated  a 
solution  of  the  two  salts  is  obtained.  The  solution  is  evapo- 


334  ELEMENTS   OP   MODERN   CHEMISTRY. 

rated,  and  the  dry  residue  moderately  calcined.  The  ferrous 
sulphate  decomposes,  yielding  sulphuric  acid,  which  distils,  and 
ferric  oxide,  which  remains  mixed  with  the  zinc  sulphate.  The 
residue  being  exhausted  with  water,  the  zinc  sulphate  dissolves 
and  is  deposited  in  crystals  on  the  cooling  of  the  concentrated 
solution. 

The  salt  may  be  prepared  in  the  laboratory  by  dissolving 
zinc  in  dilute  sulphuric  acid :  it  is  the  residue  in  the  prepara- 
tion of  hydrogen. 

Sulphate  of  zinc  crystallizes  with  7  molecules  of  water.  In 
this  state  it  occurs  as  right  rhombic  prisms,  isomorphous  with 
magnesium  sulphate. 

When  heated,  it  melts  in  its  water  of  crystallization,  of 
which  it  loses  6  molecules  ;  the  seventh  it  abandons  only  at 
238°. 

At  a  high  red  heat  it  is  decomposed  into  zinc  oxide,  sul- 
phurous oxide,  and  oxygen. 

Zinc  sulphate  is  very  soluble  in  water,  of  which  100  parts 
dissolve  48.36  parts  of  the  anhydrous  salt  at  10°,  and  95.6 
parts  at  100°.  The  solution  has  a  styptic  taste. 

Zinc  sulphate  forms  crystallizable  double  salts  with  the  alka- 
line sulphates ;  thus,  there  is  a  double  sulphate  of  zinc  and 
potassium,  containing 

ZnS04.K2SO*  +  6H20 

Characters  of  Zinc  Salts. — The  zinc  salts  are  colorless 
unless  the  corresponding  acid  be  colored.  Their  neutral  solu- 
tions are  partially  decomposed  by  hydrogen  sulphide,  which 
precipitates  white  sulphide  of  zinc ;  the  addition  of  a  mineral 
acid  prevents  the  precipitation ;  the  zinc  salts  of  organic  acids, 
such  as  the  acetate  and  lactate,  are  completely  decomposed  by 
hydrogen  sulphide. 

Ammonium  sulphide  produces  a  white  precipitate  of  sul- 
phide; this  reaction  is  characteristic. 

Potassium  and  sodium  hydrates,  and  also  ammonia,  form 
white  precipitates,  soluble  in  an  excess  of  the  reagent. 

Potassium  ferrocyanide  gives  a  white  precipitate. 


GALLIUM.  335 

GALLIUM. 

Ga  =  69.9 

This  metal  was  discovered  in  1876  by  Lecoq  de  Boisbaudran. 
It  is  contained  in  small  quantity  in  certain  blendes.  One  of 
the  richest,  found  in  Westphalia,  contains  only  one  sixty-thou- 
sandth of  its  weight. 

In  order  to  extract  the  gallium,  the  ore  is  roasted,  and  the 
product  dissolved  in  sulphuric  acid.  An  acid  liquor  is  thus 
obtained,  containing  principally  sulphate  of  zinc,  with  sulphates 
of  iron,  aluminium,  indium,  etc.,  and  a  trace  of  gallium  sul- 
phate. 

The  following  reactions  are  employed  by  Lecoq  de  Bois- 
baudran and  Jungfleisch  for  the  separation  of  the  gallium : 

1.  When  the  liquid  is  neutralized,  the  ferric  oxide,  alumina, 
and  gallium  oxide,  which  is  a  sesquioxide,  are  precipitated. 
The  precipitate  is  redissolved  in  sulphuric  acid,  and  the  same 
operation  repeated  after  converting  the  ferric  oxide  into  ferrous 
oxide,  which  remains  dissolved  in  the  neutral  liquid.     By  this 
means  the  greater  part  of  the  iron  is  removed. 

2.  Gallium  oxide  dissolves,  like  alumina  and  zinc  oxide,  in 
an  excess  of  potassium  hydrate  ;  when  this  solution  is  saturated 
with  hydrogen  sulphide,  the  zinc   is  precipitated  as  sulphide, 
while  the  gallium  and  aluminium    remain  in  solution.      The 
greater  part  of  the  zinc  is  thus  separated. 

3.  When  water  is  added   to  a  boiling  solution  of  gallium 
sulphate,  the  latter  is  precipitated  as  subsulphate,  while  alumi- 
nium sulphate  remains  in  solution. 

4.  Gallium  oxide  dissolves  in  an  excess  of  ammonia ;  alumina 
does  not. 

5.  Gallium  separates  in  the  metallic  state  when  a  voltaic 
current  is  passed  through  an  alkaline  solution  of  gallium  oxide. 

Physical  Properties. — Gallium  has  a  metallic  lustre  recalling 
that  of  nickel.  It  readily  crystallizes  in  forms  derived  from  a 
right  rhombic  octahedron,  generally  in  magnificent  laminae.  Its 
density  is  5.96.  It  melts  at  29.5°,  and  has  a  tendency  to  re- 
main in  a  state  of  superfusion.  It  is  not  volatile. 

This  collection  of  properties  gives  to  gallium  a  special  place 
among  the  metals.  It  is  one  of  the  most  remarkable  of  recent 
discoveries. 

Chemical  Properties. — These  are  but  little  known  at  present. 


336  ELEMENTS   OF   MODERN   CHEMISTRY. 

Gallium  is  oxidized  but  little,  if  at  all,  when  heated  in  the  air 
or  in  oxygen.  It  forms  a  sesqjiioxide,  Ga*03,  which  resembles 
alumina  in  that  it  forms  alums.  Gallium  alum  was  obtained 
by  Lecoq  de  Boisbaudran. 

Gallium  combines  directly  with  chlorine,  forming  a  solid, 
crystalline,  and  very  volatile  chloride. 


INDIUM. 

In  ==  113.4 

This  metal  was  discovered  in  1863  by  Beich  and  Kichter 
in  the  zinc  blendes  of  Freiberg  (Saxony).  It  appears  to  exist 
in  the  majority  of  zinc  blendes,  and  accompanies  the  zinc  which 
is  extracted  from  those  minerals.  It  is  ordinarily  obtained 
from  metallic  zinc,  which,  however,  contains  only  very  small 
quantities  of  it.  Commercial  zinc  (that  of  Freiberg  is  prefer- 
able) is  digested  in  a  quantity  of  dilute  sulphuric  acid  insuffi- 
cient to  dissolve  all  of  the  metal ;  after  several  weeks,  a  spongy 
mass  remains,  which  contains  an  excess  of  zinc  and,  indepen- 
dently of  other  metals,  a  small  quantity  of  indium.  This  is 
the  residue  from  which  indium  is  obtained  by  processes  which 
need  not  be  here  described. 

Indium  is  a  brilliant  metal,  possessing  almost  the  lustre  of 
silver.  It  is  soft  and  ductile.  It  melts  at  176°,  and  is  vola- 
tile, but  less  so  than  zinc  and  cadmium.  It  approaches  these 
metals  in  its  general  chemical  properties,  but  is  more  electro- 
negative, both  of  the  latter  metals  precipitating  it  from  its 
solutions. 

Indium  is  characterized  by  several  spectroscopic  lines,  among 
which  are  a  very  brilliant  blue  and  a  less  marked  violet  line. 
Winkler  has  indicated  two  other  less  distinct  blue  lines. 

Two  oxides  of  indium  have  been  described,  a  sesquioxide, 
In203.  and  a  suboxide.  The  first  is  obtained  by  calcining  the 
nitrate ;  it  is  yellow.  When  heated  to  300°  in  a  current  of 
hydrogen,  it  is  partially  reduced,  yielding  a  black  suboxide. 

Indium  chloride,  In2Cl6,  is  formed  when  indium  is  heated 
in  a  current  of  chlorine.  It  is  a  snow-white,  volatile  solid. 


CADMIUM.  337 

CADMIUM. 

Cd  =  112 

Natural  State  and  Extraction, — Cadmium  is  generally 
found  associated  with  zinc,  either  as  oxide  in  calamine,  or  as 
sulphide  in  zinc  blende.  As  it  is  more  volatile  than  zinc,  it 
becomes  concentrated  in  the  first  products  of  distillation. 

It  is  found  especially,  in  the  state  of  oxide,  in  the  brown 
powder  called  cadmies,  which  condenses  during  the  first  hours 
of  the  distillation  in  the  sheet-iron  receivers  adapted  to  the  re- 
torts (Fig.  105).  When  mixed  with  powdered  charcoal  and 
calcined,  this  powder  yields  an  alloy  of  zinc  and  cadmium 
which  distils. 

The  cadmium  is  extracted  by  dissolving  the  alloy  in  dilute 
sulphuric  acid  and  passing  a  current  of  hydrogen  sulphide 
through  the  acid  liquid.  The  cadmium  is  precipitated  as  a 
yellow  sulphide.  This  sulphide  is  dissolved  in  hydrochloric 
acid  and  the  solution  of  cadmium  chloride  precipitated  by  am- 
monium carbonate.  The  cadmium  carbonate  thus  obtained  is 
calcined,  and  so  converted  into  oxide,  which  is  mixed  with 
one-tenth  its  weight  of  powdered  charcoal  and  heated  in  a  clay 
retort.  The  cadmium  distils. 

Properties. — Pure  cadmium  has  a  white  lustre,  but  soon 
tarnishes  in  the  air.  Its  density  is  8.60-8.69.  It  melts  at 
320°  (Person),  and  boils  at  860°  (H.  Deville  and  Troost).  It 
may  be  obtained  crystallized  in  octahedra. 

It  dissolves  in  dilute  sulphuric  and  hydrochloric  acids  with 
evolution  of  hydrogen. 

Cadmium  Oxide,  CdO. — The  oxide  of  cadmium  may  be  ob- 
tained by  calcining  either  the  carbonate  or  nitrate.  It  has  a 
yellowish-brown  color,  or  a  brown  more  or  less  deep.  It  is  re- 
duced at  high  temperatures  by  carbon  and  by  hydrogen,  its 
reduction  taking  place  more  readily  than  that  of  zinc  oxide. 

Cadmium  Sulphide,  CdS. — This  sulphide  occurs  in  nature 
in  the  form  of  bright  yellow,  hexagonal  prisms,  terminated  by 
six-sided  pyramids. 

It  may  be  prepared  in  the  laboratory  by  precipitating  a  solu- 
tion of  a  cadmium  salt  by  hydrogen  sulphide  or  a  soluble  sul- 
phide. An  amorphous  precipitate  of  a  fine  yellow  color  is  thus 
obtained.  In  this  form  it  is  employed  in  oil  painting. 

Cadmium  Iodide,  CdP. — This  salt  is  prepared  by  digesting 
p  29 


338  ELEMENTS   OF   MODERN   CHEMISTRY. 

finely-divided  cadmium  with  iodine  in  presence  of  water.  It 
crystallizes  from  its  aqueous  solution  in  transparent  and  color- 
less, hexagonal  prisms  having  a  brilliant  lustre.  It  is  soluble 
in  water  and  alcohol. 

Cadmium  Sulphate,  CdSO4  -f  4H20.— Cadmium  sulphate 
is  obtained  by  dissolving  the  metal,  or  its  oxide  or  carbonate,  in 
dilute  sulphuric  acid.  The  neutral  and  concentrated  solution 
deposits  the  salt  in  beautiful,  right  rectangular  prisms.  These 
crystals  are  efflorescent. 


COBALT. 

Co  =  59 

Cobalt  was  discovered  by  Brandt  in  1753.  It  is  found  prin- 
cipally in  the  state  of  arsenide,  CoAs2,  and  as  sulph-arsenide, 
CoAsS  (gray  cobalt).  Its  ores  are  worked  principally  for  the 
production  of  a  dark-blue,  vitreous  mass,  a  combination  of 
cobalt  silicate  and  potassium  silicate,  known  as  smalt  or  azure 
blue. 

The  metal  is  prepared  in  the  laboratory  by  calcining  its  oxa- 
late  in  a  covered  crucible. 

CoC20*    =     Co     +     2C02 

Cobalt  oxalate.  Carbon  dioxide. 

It  may  be  obtained  as  a  metallic  button  by  heating  the  pul- 
verulent metal  in  a  lime  crucible  in  a  wind-furnace.  The  lime 
crucible  is  placed  in  another  crucible  of  refractory  clay,  and 
the  space  between  the  two  is  filled  up  with  fragments  of  quick- 
lime (H.  Sainte-Claire  Deville). 

Pure  cobalt  is  silvery-white.  It  is  very  malleable  ;  its  den- 
sity is  8.6,  and  it  is  magnetic.  At  ordinary  temperatures  it  is 
unaffected  by  the  air,  but  at  a  red  heat  it  is  converted  into 
oxide. 

Oxides  of  Cobalt. — A  monoxide,  CoO,  and  a  sesquioxide, 
Co203,  are  known,  and  several  intermediate  oxides. 

The  monoxide  may  be  obtained  by  calcining  cobalt  carbonate 
in  close  vessels.  It  is  a  greenish-gray  or  olive-green  powder, 
which  is  reduced  by  hydrogen,  charcoal,  and  carbon  monoxide 
at  a  red  heat. 

When  heated  with  borax  before  the  blow-pipe,  it  dissolves, 
forming  a  blue  glass.  It  is  used  for  giving  a  blue  color  to 
glass  and  porcelain. 


COBALT.  339 

When  an  excess  of  potassium  hydrate  is  added  to  the  solu- 
tion of  a  salt  of  cobalt,  a  rose-red  precipitate  of  cobalt  hydrate, 
Co(OH)2,  is  formed. 

Cobalt  sesquioxide,  Co203,  is  prepared  by  passing  a  current 
of  chlorine  through  water,  holding  in  suspension  the  rose- 
colored  hydrate  above  mentioned. 

2CoO  +  H20  -f  CP  =  Co203  +  2HC1 

The  sesquioxide  is  deposited  as  a  black  powder,  which  may 
be  dried  by  carefully  heating  it. 

Cobalt  Chloride,  CoCl2. — When  pulverulent  cobalt  is  heated 
in  a  current  of  chlorine,  it  takes  fire  and  is  converted  into  a 
chloride,  which  sublimes  in  blue  scales.  A  solution  of  this 
chloride  may  be  obtained  by  dissolving  either  monoxide  or  car- 
bonate of  cobalt  in  hydrochloric  acid.  The  neutral  solution  is 
currant-red,  and  on  evaporation  deposits  hydrated  crystals  of 
the  same  color.  But  when  it  is  concentrated,  after  having 
added  hydrochloric  or  sulphuric  acid,  it  becomes  blue.  This 
change  of  color,  due  to  the  formation  of  anhydrous  chloride 
even  in  the  midst  of  the  hot  liquid,  has  caused  the  employ- 
ment of  cobalt  chloride  as  a  sympathetic  ink.  Characters 
traced  with  the  dilute  solution,  which  is  rose-colored,  are  invisi- 
ble on  white  paper,  and  appear  blue  only  when  the  paper  is 
warmed,  again  becoming  invisible  on  cooling,  by  the  absorption 
of  atmospheric  moisture. 

Cobalt  Sulphate,  CoSO4  -f  7H20.— This  salt  is  found  in 
nature,  crystallized  in  oblique  rhombic  prisms.  It  may  be  ob- 
tained by  dissolving  the  oxide  or  carbonate  in  dilute  sulphuric 
acid  and  concentrating  the  red  solution.  At  ordinary  temper- 
atures, the  latter  deposits  red  crystals,  isomorphous  with  ferrous 
sulphate.  Between  20  and  30°,  it  yields  right  rhombic  prisms, 
containing  6  molecules  of  water,  and  isomorphous  with  magne- 
sium sulphate. 

Characters  of  Cobalt  Salts. — The  cobaltous  salts  are  the 
more  important.  Their  solutions  are  rose  or  currant-red,  but 
when  concentrated  and  hot  they  become  blue,  especially  when 
an  excess  of  acid  is  present.  Hydrogen  sulphide  does  not  pre- 
cipitate solutions  of  cobalt  salts.  Ammonium  sulphide  forms 
a  black  precipitate.  Potassium  hydrate  gives  a  blue  precipitate 
of  a  basic  salt,  which,  in  presence  of  an  excess  of  potassa,  is 
converted  into  hydrate  of  cobalt,  having  a  dirty  rose  color. 


340  ELEMENTS   OF   MODERN   CHEMISTRY. 

Ammonia  forms  a  blue  precipitate,  soluble  in  an  excess  of 
the  reagent. 

When  heated  with  borax  in  the  blow-pipe  flame,  the  salts  of 
cobalt  yield  beads  of  a  pure  blue  color. 


NICKEL. 

Ni  =  59 

This  metal  was  discovered  by  Cronstedt  in  1751. 

Natural  State  and  Extraction. — Nickel  is  found  as  arsen- 
ide, NiAs2,  in  kupfernickel  or  nickeline.  In  the  preparation  of 
smalt  from  the  ores  of  cobalt,  which  always  contain  nickel,  the 
latter  metal  combines  with  the  arsenic  and  a  certain  proportion 
of  sulphur,  forming  a  metallic-looking  mass  known  as  speiss. 

In  the  arts,  nickel  is  extracted  from  kupfernickel  or  from 
speiss.  In  the  laboratory  it  is  prepared  by  reducing  the  oxide 
in  a  brasqued  crucible,  or  by  calcining  the  oxalate  out  of  con- 
tact with  the  air.  When  heated  to  whiteness  in  a  lime  cruci- 
ble the  nickel  melts  to  a  metallic  button. 

Properties. — Pure  nickel  is  grayish-white.  It  is  malleable, 
ductile,  and  very  tenacious.  Its  density  is  8.279,  and  may  be 
increased  to  8.666  by  hammering.  Next  to  manganese,  it  is 
the  hardest  of  the  metals.  It  is  less  fusible  than  iron  and  more 
fusible  than  manganese.  It  is  magnetic  at  ordinary  tempera- 
tures, but  loses  this  property  at  about  250°.  It  is  unaltered  by 
the  air  at  ordinary  temperatures,  but  absorbs  oxygen  at  a  red 
heat.  It  dissolves  slowly  in  dilute  sulphuric  and  hydrochloric 
acids,  rapidly  in  nitric  acid.  In  contact  with  concentrated  nitric 
acid  it  becomes  passive  like  iron. 

Nickel  is  used  in  the  arts,  in  the  manufacture  of  an  alloy 
known  as  German  silver,  which  contains  50  per  cent,  of  copper, 
25  of  nickel,  and  25  of  zinc. 

Nickel  may  be  deposited  as  a  brilliant  metallic  layer  by  the 
electrolysis  of  a  solution  of  nickel  and  ammonium  double  sul- 
phate (A.  C.  and  E.  Becquerel).  Adams  made  an  application 
of  this  property  to  the  nickel-plating  of  various  objects  by 
electro-metallurgy,  and  the  process  is  now  largely  employed. 

Oxides  of  Nickel. — A  monoxide,  NiO,  and  a  sesquioxide, 
Ni203,  are  known. 

The  anhydrous  monoxide  is  an  ash-gray  powder.  It  is 
obtained  by  strongly  calcining  the  nitrate  or  carbonate.  On 


NICKEL.  341 

adding  potassium  hydrate  to  a  nickel  salt,  an  apple-green  pre- 
cipitate of  nickel  hydrate,  Ni(OH)2,  is  formed. 

Nickel  sesquioxide  may  be  obtained  by  moderately  calcining 
the  nitrate.  It  is  black.  When  chlorine  gas  is  passed  into 
water  holding  nickel  hydrate  in  suspension,  a  dark-brown  pow- 
der is  obtained,  which  is  a  hydrate  of  the  sesquioxide.  This 
hydrate  may  also  be  made  by  precipitating  a  nickel  salt  with 
potassium  hydrate  mixed  with  an  alkaline  hypochlorite. 

When  strongly  calcined,  nickel  sesquioxide  abandons  part  of 
its  oxygen  and  is  changed  into  monoxide.  Treated  with  hydro- 
chloric acid,  it  yields  nickel  chloride,  and  chlorine  is  disengaged. 

Ni203  +  6HC1  =  2NiCl2  +  3H20  +  Cl2 

Nickel  Chloride,  NiCl2. — This  salt  may  be  obtained  anhy- 
drous by  the  action  of  chlorine  on  nickel-filings  ;  it  is  volatile 
at  a  dull-red  heat,  and  sublimes  in  golden-yellow  scales.  The 
hydrated  chloride  is  formed  by  the  action  of  boiling  water  on 
the  anhydrous  salt,  or  by  the  action  of  hydrochloric  acid  on  the 
oxide  or  carbonate.  Its  solution  is  green,  and  after  proper 
concentration  deposits  beautiful  green  crystals  which  contain 
NiCl2  4-  9H2O. 

Nickel  Sulphate,  NiSO  -}-  7H20.— The  sulphate  is  depos- 
ited in  fine,  emerald-green,  orthorhombic  prisms,  isomorphous 
with  magnesium  sulphate,  when  its  solution  is  allowed  to  evap- 
orate spontaneously  below  15°.  There  is  another  hydrate  con- 
taining 6H20,  which  is  dimorphous.  When  deposited  between 
20  and  30°,  it  crystallizes  in  square  octahedra,  but  when  its 
solution  is  made  to  crystallize  between  60  and  70°,  right  rhom- 
bic prisms  are  obtained,  isomorphous  with  the  corresponding 
sulphates  of  magnesium,  zinc,  and  cobalt. 

Nickel  sulphate  dissolves  in  3  times  its  weight  of  water  at  10°. 

Characters  of  Nickel  Salts. — The  nickel  salts  when  hy- 
drated or  in  solution  have  a  fine  emerald-green  color.  When 
anhydrous  they  are  yellow. 

Hydrogen  sulphide  does  not  precipitate  them  from  acid  solu- 
tions. Ammonium  sulphide  throws  down  a  black  precipitate. 
Potassium  hydrate  and  potassium  carbonate  form  apple-green 
precipitates. 

In  neutral  solutions,  ammonia  gives  a  green  precipitate  of 
nickel  hydrate,  which  dissolves  in  an  excess  of  ammonia,  form- 
ing a  blue  solution. 

29* 


342  ELEMENTS   OF   MODERN   CHEMISTRY. 

MANGANESE. 

Mn  =  55 

This  metal  has  been  obtained  as  a  coherent,  very  hard  mass, 
by  reduction  of  either  manganous  carbonate  or  red  oxide  of 
manganese  with  charcoal  or  sugar  in  a  lime  crucible  at  the 
highest  heat  of  a  wind-furnace  (H.  Deville). 

It  is  whitish-gray,  and  almost  as  infusible  as  platinum.  Its 
density  is  7.2.  Its  powder  decomposes  warm  water. 

MANGANESE   OXIDES. 

Manganese  forms  six  compounds  with  oxygen  : 

Manganous  oxide MnO 

Manganoso-manganic  oxide Mn80* 

Manganic  oxide Mn203 

Manganese  dioxide MnO2 

Manganic  anhydride MnO3 

Permanganic  anhydride Mn207 

Manganous  oxide  is  formed  when  manganous  carbonate  is 
strongly  heated  in  a  current  of  hydrogen.  Carbon  dioxide  is 
evolved,  and  a  green  powder,  which  is  manganous  oxide,  re- 
mains, It  takes  fire  on  contact  with  an  incandescent  body,  and 
is  converted  into  a  brownish-red  powder,  which  is  red  oxide  of 
manganese, 

3MnO  +  0  =  Mn3O 

The  latter  body  is  also  formed  by  the  calcination  of  the  diox- 
ide. It  is  analogous  to  the  magnetic  oxide  of  iron,  and  con- 
stitutes the  mineral  known  as  hausmannite. 

Manganic  oxide,  Mn208,  occurs  in  nature  in  the  crystallized 
state  as  braunite.  It  is  isomorphous  with  alumina  and  ferric 
oxide. 

MANGANESE  DIOXIDE. 

(BINOXIDE  OR  PEROXIDE  OF  MANGANESE.) 
MnO2 

This  important  body  is  found  abundantly  in  nature ;  it  con- 
stitutes the  mineral  pyrolusite.  It  may  be  obtained  pure  and 
anhydrous  by  exposing  a  concentrated  solution  of  manganous 
nitrate  to  heat  and  gradually  raising  the  temperature  to  155°. 


MANGANIC   ACID.  343 

Nitrous  vapors  are  evolved,  and  a  brilliant  brown-black  mass  is 
obtained,  which  is  the  dioxide. 

Mn(N03)2  =  MnO2  +  2N02 

It  loses  one-third  of  its  oxygen  when  heated  to  redness,  and 
is  converted  into  the  red  oxide.  When  heated  with  concen- 
trated sulphuric  acid,  it  loses  half  of  its  oxygen,  manganous 
sulphate  being  formed, 

MnO2  +  H2S04  =  MnSO4  +  H20  +  O 

With  hydrochloric  acid  it  yields  water,  chlorine,  and  manga- 
nous chloride. 

A  hydrate  of  manganese  dioxide  is  formed  when  an  excess 
of  chlorine  is  directed  into  water  holding  in  suspension  man- 
ganous hydrate  or  carbonate.  This  hydrate  is  a  dark-brown 
powder. 

Manganese  dioxide  is  largely  employed  for  the  preparation 
of  oxygen  and  chlorine.  It  is  used  to  decolorize  glass  black- 
ened by  carbonaceous  matters  or  rendered  green  by  a  trace  of 
iron. 

MANGANIC  ACID. 

When  manganese  dioxide  is  heated  with  potassium  hydrate 
in  a  silver  crucible,  and  the  calcined  mass  is  exhausted  with 
water,  the  latter  dissolves  out  potassium  manganate.  A  dark- 
green  liquor  is  thus  obtained  which,  when  evaporated  in  vacuo, 
deposits  a  crystalline  mass.  These  crystals  may  be  drained  on 
a  porous  porcelain  plate,  and  green  needles  of  potassium  man- 
ganate, K2MnO*,  remain.  The  salt  is  isomorphous  with  the 
sulphate  K2S04. 

When  the  green  solution  is  boiled,  it  becomes  red  and  deposits 
brown  flakes  of  hydrated  manganese  dioxide  :  the  red  liquor  is 
a  solution  of  potassium  permanganate,  this  salt  being  formed  at 
the  expense  of  the  manganate,  which  breaks  up  into  hydrated 
dioxide,  potassium  hydrate,  and  permanganate. 

3K*MnO*  -f  3H20  =  K2Mn208  -f  Mn02.H2O  +  4KOH 

Potassium  Potassium         Hydrated  manganese 

manganate.  permanganate.  dioxide. 

An  analogous  decomposition  takes  place  when  an  acid  is 
added  to  the  green  solution  of  manganate;  a  manganous  salt 
and  permanganic  acid  are  formed,  and  the  latter  colors  the 
liquid  red. 


344  ELEMENTS   OP   MODERN   CHEMISTRY. 


PERMANGANIC   ACID. 

Potassium  permanganate,  K2Mn208,  is  an  important  salt.  It 
may  be  prepared  by  introducing  into  an  iron  crucible  5  parts 
of  caustic  potassa  with  a  small  quantity  of  water,  then  a  mix- 
ture of  3?  parts  of  potassium  chlorate  and  4  parts  of  finely- 
powdered  manganese  dioxide.  The  mixture  is  heated  and 
continually  stirred,  until  the  mass  becomes  dry  and  the  tem- 
perature has  reached  dull  redness.  After  cooling,  the  product 
is  pulverized  and  introduced  into  200  parts  of  boiling  water. 
When  the  liquid  has  assumed  a  purple  color,  it  is  allowed  to 
stand,  decanted,  and  after  neutralization  by  nitric  acid,  is 
evaporated  at  a  gentle  heat.  On  cooling,  it  deposits  crystals 
that  may  be  dried  on  a  porous  tile. 

Potassium  permanganate  crystallizes  in  almost  black  needles, 
having  a  metallic  reflection.  It  dissolves  in  15  or  16  parts  of 
cold  water,  and  its  solution  has  a  magnificent,  intense  purple 
color. 

If  solution  of  sulphurous  acid  be  added  to  potassium  per- 
manganate solution,  the  latter  is  instantly  decolorized,  and  the 
liquid  contains  only  potassium  sulphate  and  manganese  sulphate. 

If  a  drop  of  the  solution  of  potassium  permanganate  be 
placed  upon  a  sheet  of  paper,  it  loses  its  color  and  a  brown 
stain  of  hydrated  manganese  dioxide  is  produced. 

These  experiments  indicate  the  oxidizing  properties  of  the 
permanganate.  In  the  first,  sulphurous  acid  was  oxidized ;  in 
the  second,  it  was  paper,  of  which  the  carbon  and  hydrogen 
removed  the  oxygen  from  the  permanganate,  which  was  thus 
reduced  to  dioxide. 


MANGANOUS  SULPHATE. 
MnSCM  +  7H20 

This  salt  may  be  prepared  by  dissolving  manganous  carbon- 
ate in  sulphuric  acid.  The  properly  concentrated  rose-colored 
solution  deposits,  between  0  and  6°,  oblique  rhombic  prisms, 
isomorphous  with  green  vitriol  and  containing  7  molecules  of 
water. 

Between  7  and  20°,  manganous  sulphate  crystallizes  with  5 


MANGANOUS  CARBONATE.  345 

molecules  of  water,  like  cupric  sulphate,  with  which  it  is  then 
isomorphous. 

Between  20  and  30°,  it  is  deposited  in  oblique  rhombic 
prisms,  according  to  Marignac,  which  contain  only  4  molecules 
of  water. 

All  of  these  crystals  are  rose-colored,  and  their  color  is 
deeper  as  they  contain  more  water  of  crystallization.  They  are 
very  soluble  in  water. 


MANGANOUS   CARBONATE. 


The  residues  from  the  preparation  of  chlorine  may  be  used 
for  making  this  salt.  They  are  evaporated,  without  filtering, 
in  a  porcelain  capsule,  with  frequent  stirring,  and  the  dry 
residue  is  calcined  with  an  excess  of  manganese  dioxide.  The 
ferric  chloride  which  was  mixed  with  the  manganous  chloride 
is  decomposed  or  volatilized  during  this  operation.  Ferric 
oxide  remains,  mixed  with  the  excess  of  manganese  dioxide 
and  the  manganous  chloride,  which  resists  the  heat.  The  latter 
is  extracted  by  exhausting  the  mass  with  boiling  water.  A 
rose-colored  solution  is  thus  obtained  which  often  contains  a 
small  quantity  of  cobalt  chloride.  The  latter  is  precipitated 
as  sulphide  by  adding  little  by  little  a  solution  of  sodium  sul- 
phide. As  soon  as  the  precipitate,  which  is  at  first  blackish, 
begins  to  assume  a  flesh  tint,  the  liquid  is  filtered  and  precipi- 
tated by  sodium  carbonate. 

Manganese  carbonate  constitutes  a  white  powder  with  a  pale 
rose  tint.  When  heated  in  contact  with  air,  it  gives  up  car- 
bonic acid  gas  and  is  converted  into  red  oxide  of  manganese. 

Characters  of  Manganese  Salts.  —  The  salts  of  manganese 
are  colorless  or  have  a  light  rose  color.  Their  solutions  are 
not  precipitated  by  hydrogen  sulphide.  Ammonium  sulphide 
gives  a  flesh-colored  precipitate  ;  sodium  carbonate,  a  dirty 
white.  Potassium  hydrate  produces  a  dirty  white  precipitate 
of  manganous  hydrate,  which  rapidly  becomes  brown  by  ab- 
sorbing oxygen  from  the  air. 

When  heated  in  the  blow-pipe  flame  with  a  small  quantity 
of  potassium  hydrate  or  nitrate,  the  salts  of  manganese  give  a 
bead  which  dissolves  in  water  with  a  green  color  (manganate). 
p* 


346  ELEMENTS   OF   MODERN   CHEMISTRY. 


CHROMIUM. 

Cr  =  52.5 

Chromium  was  discovered  in  1797,  by  Vauquelin,  in  a  min- 
eral formerly  known  as  red  lead  of  Siberia,  and  which  is 
chromate  of  lead.  It  forms  one  of  the  elements  of  chrome 
iron,  a  combination  of  chromium  oxide  with  ferrous  oxide, 
Cr2O3.FeO,  which  corresponds  to  magnetic  oxide  of  iron, 
Fe2O3.FeO. 

H.  Deville  isolated  the  metal  by  calcining  chromium  oxide 
with  charcoal  and  linseed  oil  in  crucibles  of  lime  and  charcoal. 
Thus  prepared,  chromium  forms  grayish- white,  metallic  grains, 
which  are  brittle,  as  hard  as  corundum,  and  have  a  density  of 
5.9. 

This  metal  does  not  oxidize  in  the  air  at  ordinary  tempera- 
tures. At  a  red  heat,  it  is  converted  into  the  oxide  (VO3. 
When  thrown  into  potassium  chlorate  in  a  state  of  fusion,  it 
burns  with  a  dazzling  white  flame,  a  chromate  being  formed. 
It  burns  in  the  same  manner  in  chlorine  gas,  being  transformed 
into  a  violet  chloride.  It  dissolves  in  hydrochloric  acid,  disen- 
gaging hydrogen. 

COMPOUNDS  OF  CHROMIUM  AND  OXYGEN. 

There  are  two  well-defined  compounds  of  chromium  and 
oxygen,  the  green  oxide  of  chromium,  Cr203,  and  chromic 
anhydride,  CrO3. 

Chromium  Oxide,  Cr2O3,  is  a  green  powder;  it  may  be 
obtained  by  calcining  mercurous  chromate. 

2Hg2Cr04  =  4Hg  -f  O5  +  Cr203 

Another  process  consists  in  heating  in  a  crucible  a  mixture 
of  2  parts  of  potassium  dichromate  with  a  little  more  than  1 
part  of  flowers  of  sulphur.  After  cooling,  the  mass  is  treated 
with  water,  which  dissolves  out  potassium  sulphate  and  leaves 
chromium  oxide. 

Fremy  obtained  it  in  small  crystals  by  passing  chlorine  gas 
over  potassium  chromate  heated  to  redness,  and  exhausting  the 
cooled  mass  with  water. 

Chromium  oxide  is  undecomposable  by  heat,  and  melts  only 
at  the  temperature  of  the  forge.  It  forms  several  different 


CHROMIC   ANHYDRIDE — CHROMATES.  347 

hydrates.  When  ammonia  is  added  to  the  green  solution  of 
chromic  chloride,  a  green,  flaky  precipitate  of  chromic  hydrate 
is  formed;  it  is  soluble  in  acids  and  in  potassium  hydrate. 

Chromic  Anhydride,  CrO3,  is  prepared  by  gradually  adding 
to  a  cold  saturated  solution  of  potassium  dichromate  1?  times 
its  volume  of  sulphuric  acid.  The  chromic  anhydride,  ordina- 
rily called  chromic  acid,  set  free  separates  in  needle-shaped 
crystals  of  a  dark-red  color,  which  should  be  drained  and  re- 
crystallized  in  a  small  quantity  of  warm  water. 

It  is  deliquescent;  its  aqueous  solution  has  a  dark  yellow- 
brown  color.  It  is  an  energetic  oxidizing  agent.  Hydrochlo- 
ric acid  converts  it  into  chromic  chloride,  with  evolution  of 
chlorine. 

2O03  -f-  12HC1  =  O2C16  +  6H20  +  3C12 

If  a  concentrated  solution  of  sulphurous  acid  be  added  to  a 
solution  of  chromic  acid,  the  liquid  immediately  becomes  green 
from  the  formation  of  chromic  sulphate. 

Chromates. — The  most  important  chromates  are  those  of 
potassium  and  lead. 

Potassium  neutral  chromate,  K2CrO*,  crystallizes  in  lemon- 
yellow,  right  rhombic  prisms,  isomorphous  with  potassium  sul- 
phate. It  is  very  soluble  in  water,  to  which  it  communicates 
an  intense  yellow  color.  So  great  is  its  coloring  property,  that 
one  part  of  chromate  will  sensibly  color  40,000  parts  of  water. 

Potassium  dichromate,  K2Cr207,  is  prepared  by  heating  to 
redness  2  parts  of  chrome  iron  with  1  part  of  nitre.  The  mass 
is  exhausted  with  water,  which  dissolves  out  potassium  neutral 
chromate;  acetic  acid  is  added  to  this  solution,  precipitating 
the  silica,  which  is  derived  from  the  crucible  and  remains  in 
the  solution  as  silicate,  and  removing  one-half  of  the  potassium 
from  the  chromate,  thus  converting  it  into  the  dichromate. 
The  latter  crystallizes  out  on  evaporation. 

Potassium  dichromate  is  a  beautiful  salt  of  an  orange-red 
color.  It  crystallizes  in  quadrangular  tables  derived  from  a 
dissymetric  prism. 

It  dissolves  in  8  or  10  parts  of  cold  water  and  in  a  much 
less  quantity  of  boiling  water. 

A  strong  heat  decomposes  it  into  neutral  chromate,  chromium 
oxide  and  oxygen. 

2K2Cr207  =  2K2O04  +  Cr203  -f  O3 


348  ELEMENTS   OP   MODERN   CHEMISTRY. 

When  heated  with  sulphuric  acid,  it  loses  oxygen  and  is 
converted  into  chromic  sulphate  and  potassium  sulphate. 

K2GV07  +  4H2S04  =  Cr2(S04)3  +  K2SO  +  4H20  +  O3 

The  residue  when  exhausted  with  water  yields  a  green  solu- 
tion, which  deposits  on  evaporation  beautiful  octahedral  crystals 
of  a  violet-black  color,  constituting  chrome  alum. 

Cr2(S04)3.K2S04  +  24H20 

Sulphurous  acid  reduces  potassium  dichromate  in  the  cold, 
also  yielding  chrome  alum  if  sulphuric  acid  be  added. 

K2Cr207  -f  3S02  +  IFSO4  =  O2(S04)3.K2SO4  -f  H20 

The  constitution  of  potassium  dichromate  is  represented  by 
the  formula 

KOCrO2 


KOCrO2 

COMPOUNDS  OF   CHROMIUM  AND   CHLORINE. 

Several  combinations  of  chromium  and  chlorine  are  known. 
The  most  important  is  the  violet  chloride,  Cr2Cl6,  correspond- 
ing to  aluminium  chloride  and  ferric  chloride.  It  is  prepared 
by  passing  chlorine  gas  over  an  intimate  and  perfectly  dry 
mixture  of  chromium  oxide  and  charcoal,  heated  to  redness  in 
a  porcelain  tube  ;  carbon  monoxide  is  disengaged,  and  chromic 
chloride  sublimes  into  the  cooler  portion  of  the  tube  in  brilliant 
peach-blossom-colored  scales. 

These  crystals  are  almost  insoluble  in  cold  water,  and  dis- 
solve but  slowly  in  boiling  water.  Hydrogen  reduces  them  at  a 
red  heat,  with  formation  of  hydrochloric  acid,  and  a  chloride, 
Cr2Cl4,  which  crystallizes  in  white  scales  (Peligot). 

Cr2Cl6  +  H2  =  2HC1  -f  Ci*Cl4 

If  a  small  quantity  of  the  chloride  Cr2Cl4,  be  added  to  hot 
water,  holding  in  suspension  the  violet  chloride,  Cr2Cl6,  the 
latter  will  be  instantly  dissolved,  forming  a  green  solution. 

Chlorochromic  anhydride,  Cr02Cl2,  is  obtained  by  heating  a 
previously  fused  mixture  of  common  salt  and  potassium  di- 
chromate with  sulphuric  acid  ;  abundant  red  vapors  are  disen- 


BISMUTH.  349 

gaged,  and  condense  to  a  blood-red  liquid.  This  body  boils 
at  116.8°.  Its  density  at  25°  is  1.920  (Thorpe).  On  contact 
with  water  it  decomposes  into  hydrochloric  acid  and  chromic 
anhydride. 

O02C12  +  IPO  =  CrO3  -f  2HC1 


BISMUTH. 

Bi  =  210 

Extraction. — This  metal  is  found  native  in  a  quartzy  gangue. 
It  is  extracted  by  simply  heating  the  mineral  in  cast  or  sheet 
iron  tubes,  which  are  arranged  in  an  inclined  position  in  a  fur- 
nace. The  bismuth  melts  and  runs  out  at  an  opening  in  the 
lower  end  of  the  tubes. 

The  bismuth  of  commerce  is  never  pure  ;  it  contains  traces 
of  other  metals,  nearly  always  of  arsenic  and  sometimes  of 
sulphur.  It  is  purified  by  pulverizing  it,  mixing  it  with  -^ 
its  weight  of  potassium  nitrate,  and  heating  the  mixture  to 
redness  in  a  clay  crucible.  The  foreign  metals  more  oxidiza- 
ble  than  the  bismuth  are  thus  converted  into  oxides,  the  ar- 
senic into  arsenate  of  potassium,  and  the  sulphur  into  potassium 
sulphate.  This  treatment  may  be  repeated  a  second  time  if 
necessary. 

Properties. — Bismuth  is  a  whitish-gray  metal,  having  a  yel- 
low lustre.  Its  fracture  is  crystalline  and  laminated.  Its  den- 
sity is  9.83,  and  it  melts  at  264°.  On  cooling,  it  crystallizes 
in  rhombohedra,  of  which  the  surfaces  become  covered  with  a 
thin  film  of  oxide,  causing  a  beautiful  iridescent  play  of  colors 
like  that  on  a  soap-bubble. 

Bismuth  increases  in  volume  on  solidifying.  It  volatilizes  at 
a  white  heat.  It  is  unaltered  by  the  air  at  ordinary  tempera- 
tures, but  at  a  red  heat  it  absorbs  oxygen  and  burns,  forming 
bismuth  oxide.  Its  best  solvent  is  nitric  acid,  which  converts 
it  into  nitrate. 

The  various  compounds  of  bismuth  present  great  analogy  to 
those  of  antimony,  next  to  which  this  metal  might  be  placed 
in  the  group  including  nitrogen,  phosphorus,  arsenic,  antimony, 
and  bismuth. 

30 


350  ELEMENTS   OF   MODERN   CHEMISTRY. 

This  analogy  is  shown  in  the  following  synoptic  table : 
Bid3  SbCP 

Bismuth  trichloride.  Antimony  trichloride. 

Bi203  Sb203 

Bismuth  trioxide.  Antimony  trioxide. 

Bi205  Sb205 

Bismuthic  anhydride.  Antimouic  anhydride. 

Bi20*  Sb204 

Bismuth  bismuthate.  Antimony  antimonate. 

Bi2S3  Sb2S3 

Bismuth  trisulphide.  Antimony  trisulphide. 

Otherwise,  bismuth  is  related  to  the  metals  proper,  not  only 
by  its  properties,  but  by  the  facility  with  which  it  forms  defi- 
nite salts.  It  is  triatomic  in  its  more  important  combinations, 
the  oxide,  chloride,  and  nitrate. 

BISMUTH    TRIOXIDE. 

Bi2O3 

This  body  is  obtained  by  decomposing  the  nitrate  by  heat. 
It  is  a  straw-yellow  powder,  fusible  at  a  red  heat,  and  yielding 
on  cooling  a  dark-yellow,  vitreous  mass.  It  attacks  clay  cruci- 
bles even  more  rapidly  than  litharge. 

A  hydrated  oxide  of  bismuth  is  formed  when  the  nitrate  or 
subnitrate  is  treated  with  potassium  hydrate  or  ammonia.  It 
is  a  white  powder,  insoluble  in  an  excess  of  alkali,  and  when 
boiled  with  potassa,  is  converted  into  the  crystalline  anhydrous 
oxide. 

BISMUTH    TRICHLORIDE. 

BiCl3 

Finely-divided  bismuth  will  burn  in  chlorine,  being  con- 
verted into  chloride.  The  latter  is  prepared  by  directing  a 
current  of  chlorine  upon  melted  bismuth  contained  in  a  retort. 
The  chloride  distils  and  solidifies  in  the  receiver  to  a  fusible, 
crystalline,  and  deliquescent  mass,  formerly  known  as  butter 
of  bismuth.  A  crystallized,  hydrated  chloride  of  bismuth  may 
also  be  obtained  by  evaporating  a  solution  of  bismuth  in  nitro- 
hydrochloric  acid. 

Bismuth  chloride  dissolves  in  water  charged  with  hydro- 
chloric acid,  but  is  decomposed  when  treated  with  pure  water ; 


BISMUTH    NITRATE.  351 

in  the  latter  case  an  oxychloride  is  formed  and  precipitated  as 
a  fine,  white  powder,  hydrochloric  acid  being  at  the  same  time 
formed. 

2BiCP  +  2H20  =  2BiOCl  +  4HC1 

Bismuth  oxychloride  is  known  as  pearl-white.  It  contains 
BiOCl. 

BISMUTH   NITRATE. 

Bi(NO3)3 

Bismuth  dissolves  readily  in  nitric  acid,  and  the  concentrated 
solution  deposits  large,  four-sided  prisms,  which  are  colorless 
and  deliquescent.  They  contain  Bi(N03)3  -f  3H*0.  They 
are  very  soluble  in  water  acidulated  with  nitric  acid,  but  if  this 
solution  be  poured  into  a  large  excess  of  water,  a  pulverulent, 
white  precipitate  is  formed,  and  increases  in  volume  if  very 
dilute  ammonia  be  gradually  added  to  the  liquid  in  order  to 
partly  neutralize  the  free  acid. 

This  precipitate  is  much  employed  in  medicine  under  the 
name  of  subnitrate  of  bismuth.  Its  composition  is  generally 
expressed  by  the  formula  BiNO*  -f  H2O  =  (BiO/NO3  -j- 
H2O. 

It  may  be  regarded  as  bismuthyl  nitrate,  that  is,  nitric 
acid,  HNO3,  in  which  the  monobasic  atom  of  hydrogen  is  re- 
placed by  the  monatomic  group  BiO.  Or  it  may  be  considered 
as  a  derivative  of  orthonitric  acid,  H3N04,  corresponding  to 
orthophosphoric  acid,  H3PO4  (page  191). 

Boiling  water  removes  still  more  nitric  acid  from  this  sub- 
nitrate,  leaving  a  residue,  which  is  used  as  a  cosmetic,  known  as 
blanc  de  fard. 

Characters  of  Solutions  of  Bismuth. — When  mixed  with 
X  large  quantity  of  water,  bismuth  solutions  give  white  pre- 
cipitates of  sub-salts.  Hydrogen  sulphide,  and  the  soluble 
sulphides  form  a  brown  precipitate  of  bismuth  sulphide,  insolu- 
ble in  an  excess  of  ammonium  sulphide.  The  alkaline  hydrates 
and  carbonates  give  white  precipitates,  insoluble  in  an  excess 
of  the  reagent. 

Bismuth  solutions  are  not  precipitated  by  either  sulphuric 
or  hydrochloric  acid. 

When  heated  with  sodium  carbonate  in  the  reducing  flame  of 
the  blow-pipe,  compounds  of  bismuth  yield  a  metallic  globule, 
very  brittle  after  cooling. 


352 


ELEMENTS   OF    MODERN    CHEMISTRY. 


TIN. 

Sn  (Stannum)=  118 

Natural  State  and  Extraction.  —  The  only  mineral  of  tin 
which  is  worked  is  the  dioxide  (cassiterite).  It  is  found  in 
veins  in  the  oldest  formations,  or  disseminated  in  sand  produced 
by  their  disaggregation.  The  principal  tin  mines  are  in  India, 
in  Malacca  and  the  island  of  Banca,  in  Wales  and  in  Saxony. 
Tin  ore  generally  occurs  mixed  with  various  other  minerals, 
such  as  sulphide  and  sulph-arsenide  of  iron,  sulphides  of  copper 
and  tin,  etc.  It  is  crushed  and  washed  in  order  to  remove 
light,  earthy  matters,  and  then  roasted.  The  sulphides  and 
sulph-arsenides  are  thus  oxidized  and  disintegrated,  and  the 

product  is  submitted  to  a  sec- 
ond washing  which  removes 
the  lighter  oxides,  leaving  the 
cassiterite.  The  latter  is  then 
heated  with  charcoal  in  a 
cupola-furnace,  represented  in 
Fig.  108;  it  is  a  sort  of  pris- 
matic furnace,  having  a  hearth 
at  the  bottom  where  the  melted 
metal  collects.  Air  is  blown 
in  through  the  tuyere  D.  Car- 
bon monoxide  is  formed,  and 
this  reduces  the  stannic  oxide  ; 
the  tin  collects  on  the  hearth, 
from  which  it  is  drawn  into 
the  basin  I,  where  it  is  stirred 
with  rods  of  green  wood.  The 
steam  and  gases  produced  by 


FIG.  108. 


the  carbonization  of  the  wood,  agitate  the  melted  mass  and  bring 
to  the  surface  the  foreign  matter  or  dross,  which  is  removed. 
The  tin  is  then  run  into  moulds. 

Thus  obtained,  tin  generally  contains  small  quantities  of 
copper,  iron,  lead,  antimony,  and  arsenic.  It  is  purified  by 
slowly  heating  it  on  the  hearth  of  a  reverberatory  furnace; 
the  pure  tin  melts  first  and  runs  out  of  the  furnace,  while  the 
less  fusible  alloys  remain  upon  the  hearth.  This  method  of 
purification  is  called  liquation. 

Properties.  —  Pure  tin  is  a  white  metal,  resembling  silver  in 


TIN.  353 

its  color  and  lustre.  It  melts  at  228°,  and  crystallizes  when 
slowly  cooled.  Crystals  of  tin,  belonging  to  the  type  of  the 
right  square  prism,  may  also  be  obtained  by  galvanic  precipi- 
tation of  the  metal.  Their  density  is  7.178.  That  of  the 
fused  and  slowly-cooled  metal  is  7.373  (H.  Deville). 

Tin  is  ductile  and  malleable.  When  a  bar  of  tin  is  bent, 
it  produces  a  peculiar  noise  called  the  cry  of  tin. 

The  metal  is  unaltered  by  the  air,  but  when  fused,  rapidly 
becomes  covered  with  a  grayish  pellicle  of  oxide.  Tin  dis- 
solves in  concentrated  hydrochloric  acid,  disengaging  hydrogen. 
The  action  is  rapid  when  heat  is  applied. 

If  ordinary  nitric  acid  be  poured  upon  granulated  tin,  an 
energetic  action  takes  place  immediately.  The  tin  is  converted 
into  a  white  powder  of  dioxide,  and  torrents  of  red  vapors  are 
evolved. 

Very  dilute  nitric  acid  attacks  tin  almost  without  disengage- 
ment of  gas.  After  some  time  the  liquid  will  be  found  to  con- 
tain a  small  quantity  of  tin  nitrate  and  ammonium  nitrate. 
The  ammonia  is  formed  by  the  simultaneous  reduction  of  water 
and  nitric  acid  by  the  tin. 

HNO3  +  H20  =  202  +  NH3 

When  tin  is  heated  with  a  concentrated  solution  of  either 
potassium  or  sodium  hydrate,  hydrogen  is  disengaged,  and  an 
alkaline  stannate  is  formed. 

Uses  of  Tin. — Tin  enters  into  the  composition  of  bronzes; 
it  is  made  into  dishes  and  covers,  and  the  thin  foil  in  which 
various  substances,  such  as  chocolate  and  tobacco,  are  enveloped. 

Tinning  of  kitchen  vessels  consists  in  covering  them  with  a 
thin  coating  of  tin.  This  protects  the  copper  or  iron  from  the 
action  of  the  acids  which  enter  into  the  composition  of  various 
articles  of  food.  The  objects  to  be  tinned  are  first  well  cleaned 
by  rubbing  them  with  sand,  and  are  then  dipped  into  melted 
tin.  After  separating  the  excess  of  metal,  they  are  polished 
by  rubbing  with  cloths  dipped  in  sal  ammoniac. 

Tin-plate  is  sheet-iron  covered  with  a  thin  layer  of  tin.  The 
iron  is  first  dipped  into  dilute  sulphuric  acid  to  remove  the 
oxide;  it  is  then  rubbed  with  sand,  and  afterwards  plunged 
successively  into  a  bath  of  melted  tallow  and  a  bath  of  tin  covered 
with  tallow.  On  contact  with  the  iron,  the  tin  enters  into  com- 
bination, forming  a  true  alloy,  which  becomes  covered  with  a 
coating  of  pure  tin. 

30* 


354  ELEMENTS   OP   MODERN   CHEMISTRY. 

When  the  surface  of  tin-plate  is  washed  with  a  mixture  of 
hydrochloric  and  nitric  acids,  the  superficial  coat  of  tin  is  dis- 
solved, and  the  crystallized  alloy  of  tin  and  iron  is  exposed. 
This  is  called  crystallized  tin-plate. 

COMPOUNDS   OF  TIN  AND  OXYGEN. 

Tin  forms  two  compounds  with  oxygen,  stannous  oxide,  SnO, 
and  stannic  oxide,  SnO2.  The  first  is  of  but  little  importance. 
It  is  obtained  by  precipitating  a  solution  of  stannous  chloride 
by  potassium  hydrate,  and  boiling  the  precipitate,  by  which  the 
white,  stannous  hydrate  first  formed  is  converted  into  a  black 
crystalline  powder  of  stannous  oxide.  When  this  substance  is 
heated  to  250°,  it  decrepitates,  increases  in  volume,  and  becomes 
converted  into  an  olive-brown  powder,  which  is  a  dimorphous 
modification  of  the  black  oxide. 

STANNIC  OXIDE. 

SnO2 

This  body  is  found  in  nature  in  the  form  of  beautiful,  hard, 
transparent  crystals  of  a  yellowish-brown  color,  belonging  to 
the  type  of  the  square  prism. 

The  white  powder  obtained  when  the  metal  is  treated  with 
nitric  acid  is  a  stannic  hydrate,  which  plays  the  part  of  an  acid, 
and  was  named  by  Fremy  metastannic  acid.  He  attributes  to 
it  the  composition  5(H*SnO*).  It  would  be  a  polymere  of 
normal  stannic  acid. 


When  heated  to  100°,  this  hydrate  loses  half  of  its  water; 
at  a  red  heat,  it  loses  the  remainder  and  is  converted  into  stannic 
oxide. 

When  ammonia  is  added  to  an  aqueous  solution  of  stannic 
chloride,  a  white,  gelatinous  precipitate  is  formed,  constituting 
a  hydrate. 


This  is  the  stannic  acid  of  Fremy.  It  dissolves  readily  in 
hydrochloric  acid,  and  the  solution  behaves  as  would  an  aqueous 
solution  of  stannic  chloride. 

H2Sn03  +  4HC1  =  SnCl*  +  3H20 


SULPHIDES   OF   TIN — STANNOUS   CHLORIDE.  355 

It  reacts  with  the  bases,  forming   stannates  of  which  the 
general  composition  is  expressed  by  the  formula: 

R2Sn03  =  I*  1  O3 


When  heated  to  140°,  or  even  when  dried  for  a  long  time 
in  a  vacuum,  it  becomes  insoluble  in  acids. 

SULPHIDES   OF   TIN. 

Two  sulphides  of  tin  are  known  :  a  monosulphide,  SnS,  and 
a  disulphide,  SnS2.  The  first  is  obtained  by  heating  tin-filings 
with  flowers  of  sulphur :  the  product  still  contains  an  excess 
of  tin,  and  it  is  necessary  to  again  heat  it  with  a  fresh  quantity 
of  sulphur.  It  is  a  crystalline,  lead-colored  mass. 

Tin  disulphide  or  stannic  sulphide  is  prepared  by  first  making 
an  amalgam  of  12  parts  of  tin  and  6  parts  of  mercury ;  this  is 
pulverized  and  the  powder  is  mixed  with  7  parts  of  flowers  of 
sulphur  and  6  parts  of  sal-ammoniac.  The  mixture  is  intro- 
duced into  a  matrass  of  green  glass  and  gradually  heated  to 
dull  redness  on  a  sand-bath.  Sulphur,  sal-ammoniac,  sulphide 
of  mercury,  and  stannous  sulphide  are  condensed  in  the  upper 
part  of  the  matrass,  of  which  the  interior  becomes  covered  with 
a  yellow  crystalline  mass  of  stannic  sulphide.  The  presence 
of  sal-ammoniac  and  mercury,  which  volatilize  in  this  opera- 
tion, prevents  an  elevation  of  temperature,  which  would  decom- 
pose the  stannic  sulphide.  The  latter  is  carried  with  their 
vapors,  and  condenses  in  brilliant,  gold-like  scales,  which  are 
greasy  to  the  touch.  This  body  is  known  as  mosaic  gold.  It 
is  decomposed  by  a  red  heat  into  stannous  sulphide  and  sul- 
phur. It  is  used  for  coating  the  cushions  of  electric  machines. 

STANNOUS   CHLORIDE. 

SnCl2 

This  compound  may  be  prepared  anhydrous  by  heating  tin 
in  hydrochloric  acid  gas.  Hydrogen  is  evolved,  and  a  white 
or  grayish  mass  remains,  which  has  a  greasy  appearance,  and 
is  almost  transparent.  It  fuses  at  250°.  This  is  stannous 
chloride. 

When  tin  is  dissolved  in  hot,  concentrated  hydrochloric  acid 
and  the  limpid  solution  is  evaporated  and  allowed  to  cool, 
beautiful  transparent  crystals  are  obtained,  which  contain 


356  ELEMENTS   OF    MODERN    CHEMISTRY. 

SnCl2  -f-  2H20.  This  is  known  in  commerce  as  tin  salt  or  tin 
crystals. 

The  crystals  of  stannous  chloride  dissolve  in  a  small  quan- 
tity of  water,  forming  a  limpid  liquid,  but  when  treated  with 
a  large  quantity  of  water,  they  yield  a  cloudy  liquid,  which 
holds  in  suspension  a  small  quantity  of  white  oxy chloride. 
The  atmospheric  oxygen  dissolved  in  the  water  takes  part  in 
this  decomposition  of  stannous  chloride,  from  which  it  removes 
part  of  the  metal,  a  corresponding  quantity  of  stannic  chloride 
(tetrachloride)  being  formed. 

Stannous  chloride  reduces  many  oxygenized  and  chlorinated 
compounds.  It  decomposes  the  salts  of  silver  and  mercury, 
setting  free  the  metal.  It  instantly  decolorizes  the  purple 
solution  of  potassium  permanganate. 

If  a  solution  of  stannous  chloride  be  added  to  a  solution  of 
corrosive  sublimate  (mercuric  chloride),  a  white  precipitate  of 
calomel  (mercurous  chloride)  is  instantly  formed.  By  adding 
an  excess  of  stannous  chloride,  all  of  the  chlorine  may  be  re- 
moved from  the  mercuric  chloride,  and  a  gray  precipitate  of 
metallic  mercury  will  be  formed. 

Stannous  chloride  is  employed  as  a  mordant  in  dyeing. 


STANNIC  CHLORIDE  (TETRACHLORIDE  OF  TIN). 

SnCl* 

If  thin  tin-foil  be  thrown  into  a  jar  of  chlorine  gas,  the 
metal  will  take  fire,  and  in  presence  of  an  excess  of  chlorine 
will  be  converted  into  anhydrous  stannic  chloride.  This  is 
liquid,  and  gives  off  white  fumes  in  the  air.  It  was  formerly 
known  as  fuming  liquor  of  Libavius. 

It  is  prepared  by  passing  dry  chlorine  upon  tin  contained  in 
a  small  retort.  The  anhydrous  chloride  condenses  in  the  re- 
cipient in  the  form  of  a  yellow  liquid.  It  may  be  decolorized 
by  rectification  with  a  small  quantity  of  mercury,  which  removes 
the  excess  of  chlorine. 

Tin  tetrachloride  boils  at  120°.  Its  density  is  2.28.  A 
small  quantity  of  water  added  to  it  is  absorbed  with  a  hissing 
noise,  and  the  formation  of  a  crystalline  deposit  of  a  hydrate, 
SnCl*  +  5H2O. 

These  crystals  may  also  be  obtained  by  dissolving  tin  in  aqua 
regia  and  evaporating  the  solution,  or,  again,  by  passing  chlo- 


LEAD.  357 

rine  into  a  solution  of  stannous  chloride  and  concentrating  the 
solution. 

The  crystals  of  hydrated  stannic  chloride  dissolve  in  water, 
forming  a  clear  solution. 

Characters  of  Stannous  Solutions. — Brown  precipitates 
are  formed  by  both  hydrogen  sulphide  and  ammonium  sulphide ; 
the  precipitate  dissolves  in  an  excess  of  the  latter  reagent. 

Potassium  hydrate  forms  a  white  precipitate,  soluble  in  an 
excess  of  potassa ;  ammonia  yields  a  white  precipitate,  insoluble 
in  excess. 

An  excess  of  stannous  chloride  produces  a  gray  precipitate 
of  metallic  mercury  in  a  solution  of  mercuric  chloride. 

Chloride  of  gold  gives  a  purple  precipitate  (purple  of  Cas- 
sius)  in  dilute  stannous  solutions. 

Characters  of  Stannic  Solutions. — Hydrogen  sulphide  and 
ammonium  sulphide  form  yellow  precipitates,  soluble  in  a  large 
excess  of  the  latter  reagent.  Potassa,  soda,  and  ammonia, 
all  form  white  precipitates,  disappearing  in  an  excess  of  the 
reagent. 

Chloride  of  gold  does  not  precipitate  stannic  solutions. 

A  sheet  of  iron  or  zinc  will  precipitate  the  tin  from  either 
stannous  or  stannic  solutions  in  gray  scales,  which  assume  the 
metallic  lustre  when  burnished. 


LEAD. 

Pb(Plumbum)  =  207 

Treatment  of  Lead  Ores. — The  minerals  of  lead  which  are 
worked  are  the  carbonate,  and  especially  the  sulphide,  known  as 
galena. 

The  extraction  of  the  metal  from  the  carbonate  is  simple : 
it  is  heated  with  charcoal  in  a  cupola-furnace,  and  the  reduced 
lead  collects  on  the  hearth. 

Two  methods  are  employed  for  the  reduction  of  galena. 
One  consists  in  melting  the  ore  with  iron  (granulated  cast  iron). 
Sulphide  of  iron  is  formed,  and  both  it  and  the  reduced  lead 
enter  into  fusion  and  separate  from  each  other  by  virtue  of 
their  different  densities,  the  lead  being  much  the  heavier. 
This  is  the  reduction  method.  It  is  employed  for  impure  ores 
having  a  silicious  gangue. 

By  the  other  process,  known  as  the  reaction  method,  the 


358 


ELEMENTS    OP   MODERN   CHEMISTRY. 


galena  is  first  roasted,  by  which  the  sulphide  is  partially  trans- 
formed into  oxide  and  sulphate ;  the  openings  of  the  furnace 
are  now  closed  and  the  temperature  is  elevated.  The  excess 
of  sulphide  then  reacts  upon  the  oxide  and  upon  the  sulphate ; 
sulphurous  acid  gas  is  disengaged,  and  metallic  lead  is  formed. 
This  is  called  work-lead. 

PbS  +  2PbO  =  3Pb  -f  SO2 
PbS  +  PbSO4  ==  2Pb  -f-  2S02 

The  operation  is  conducted  in  a  reverberatory  furnace  repre- 
sented in  Fig.  109.     The  ore  is  spread  in  thin  layers  on  the 


3SWSSSS3W 

PIG.  109. 

hearth  E,  and  heated  to  dull  redness ;  the  fire  is  at  A,  and  the 
air  enters  by  the  openings  D.  These  are  closed  when  it  is 
judged  by  the  aspect  of  the  mass  that  the  roasting  is  suffi- 
ciently advanced.  The  heat  is  then  increased. 

Independently  of  the  portion  of  lead  sulphide  which  reacts 
upon  the  oxide  and  sulphate,  there  is  always  an  excess,  which 
melts  when  the  heat  is  increased,  and  separates  in  the  form  of 
lead  matt.  This  is  subjected  to  another  operation  by  the  same 
process  of  reaction,  and  furnishes  a  harder  lead  than  that  first 
obtained ;  it  contains  a  small  quantity  of  copper,  and  is  known 
as  slag  lead. 

In  some  works,  charcoal-powder  is  added  at  a  certain  stage 
of  the  roasting,  to  remove  the  oxygen  from  the  oxide  and  sul- 
phate formed. 


LEAD. 


359 


Treatment  of  Argentiferous  Lead. — The  lead  produced  by 
these  methods,  and  especially  the  work-lead,  often  contains  a 
small  proportion  of  silver.  In  order  to  separate  the  latter 
metal,  the  lead  is  submitted  directly  to  cupellation,  or  is  first 
refined  by  way  of  crystallization  before  the  cupellation. 

The  object  of  refining  by  crystallization  is  the  formation  of 
an  alloy  of  lead  and  silver,  richer  in  silver  than  the  work-lead. 
The  argentiferous  lead  is  melted  and  allowed  to  cool  slowly; 
nearly  pure  lead  separates  in  the  form  of  crystals,  which  are 
deposited  at  the  bottom  of  the  molten  metal.  These -are  re- 
moved by  a  ladle  as  fast  as  they  are  formed ;  the  richer  alloy 


FIG.  110. 

of  lead  and  silver  remains  liquid.  The  crystals  of  lead  still 
contain  a  little  silver,  and  are  submitted  to  another  fusion ;  lead 
again  crystallizes  out  on  cooling,  and  a  small  quantity  of  an 
alloy  still  rich  in  silver  is  obtained.  The  same  operation  re- 
peated a  third  time  determines  the  separation  of  pure  lead. 
The  alloys  of  lead  and  silver  thus  obtained  are  themselves  sub- 
mitted to  several  successive  fusions  and  crystallizations,  and  a 
still  richer  alloy  results. 

The  alloy  thus  concentrated  is  cupelled.     The  operation  con- 
sists in  melting  the  lead  in  a  reverberatory  furnace  (Fig.  110), 


360  ELEMENTS   OF   MODERN   CHEMISTRY. 

of  which  the  hearth  has  a  hemispherical  form,  and  is  called 
the  cupel.  The  vault  of  the  furnace  is  formed  by  a  sheet-iron 
cover,  G,  which  can  be  raised  and  lowered  at  will.  When  the 
lead  is  melted,  a  strong  blast  of  air  is  blown  upon  its  surface 
through  the  tuyeres  ft;  the  lead  is  thus  converted  into  oxide, 
which  melts  and,  driven  by  the  current  of  air,  flows  from  the 
cupel  through  a  notch  cut  in  its  edge  down  to  the  level  of  the 
molten  metal,  and  which  is  gradually  deepened  as  that  level 
becomes  lowered.  The  silver,  which  is  not  oxidizable,  becomes 
concentrated  in  the  cupel  as  the  lead  is  eliminated ;  and  when 
the  last  portions  of  the  latter  metal  become  oxidized,  the  sur- 
face of  the  silver  is  covered  with  only  a  thin  layer  of  fused 
litharge,  which  breaks  up  suddenly  and  displays  the  brilliant 
surface  of  the  metal.  This  phenomenon,  called  brightening, 
indicates  the  termination  of  the  operation. 

The  oxide  of  lead  formed  first  in  the  cupellation  of  work- 
lead  is  called  abstrich.  It  is  black,  and  still  contains  a  little 
silver,  as  well  as  copper  and  antimony  (Berthier).  The  oxide 
which  flows  out  after  the  abstrich  is  litharge. 

Properties  of  Lead. — Lead  is  a  bluish-white  metal,  having 
a  certain  degree  of  lustre  when  its  surface  is  freshly  cut.  It 
is  the  softest  and  least  tenacious  of  all  the  common  metals.  It 
can  easily  be  cut  with  a  knife  and  scratched  by  the  finger-nail. 
It  may  readily  be  reduced  to  thin  sheets,  but  is  not  easily  drawn 
into  wire.  Its  density  is  11.363  (H.  Deville).  It  melts  be- 
tween 326  and  334°,  and  volatilizes  at  a  white  heat.  It  may 
sometimes  be  obtained  crystallized  in  regular  octahedra  by 
allowing  a  large  quantity  of  molten  lead  to  cool  slowly,  and 
decanting  the  still  liquid  portion. 

The  brilliant  surface  of  lead  tarnishes  in  the  air.  When 
melted,  it  rapidly  absorbs  oxygen  and  becomes  covered  with  a 
pellicle  of  oxide,  which  is  transformed  by  the  prolonged  action 
of  heat  into  a  yellow  powder,  known  as  massicot. 

On  contact  with  aerated  water,  lead  absorbs  oxygen  and  car- 
bon dioxide,  and  becomes  covered  with  a  thin  layer  of  carbon- 
ate. This  fact  explains  the  presence  of  traces  of  lead  in  rain- 
water which  has  been  collected  from  lead  gutters,  or  kept  in 
leaden  reservoirs. 

The  presence  of  small  quantities  of  sulphates  and  chlorides 
in  water  prevents  this  oxidation  of  lead,  so  that  the  metal  can 
be  used  without  danger  for  the  distribution  of  most  spring  and 
river  waters. 


LEAD    MONOXIDE.  361 

Lead  is  rapidly  dissolved  by  concentrated  and  boiling  hydro- 
chloric acid.  Dilute  sulphuric  acid  does  not  attack  it;  the 
boiling  concentrated  acid  converts  it  into  sulphate  with  evolu- 
tion of  sulphurous  acid  gas.  Nitric  acid  attacks  and  dissolves 
it  at  ordinary  temperatures,  disengaging  red  vapors  and  forming 
lead  nitrate. 

Lead  and  its  compounds  are  poisonous.  Its  effects  on  the 
economy  are  especially  manifested  after  the  long-continued 
absorption  of  very  small  quantities  of  the  metal,  of  which  the 
accumulation  in  the  system  is  made  evident  by  various  symp- 
toms; the  best  known  is  lead  colic  or  painter 's  colic.  Plumbers, 
glaziers  of  pottery,  painters,  color-grinders,  and  the  workmen 
employed  in  the  manufacture  of  minium,  or  red  lead,  white 
lead,  etc.,  are  exposed  to  this  chronic  poisoning.  The  soluble 
sulphates  are  antidotes  for  acute  cases  of  poisoning,  and  potas- 
sium iodide  causes  the  elimination  of  lead  from  the  system  in 
chronic  cases. 

Uses  of  Lead. — This  metal  is  used  for  the  manufacture  of 
shot,  and  pipes  for  the  distribution  of  water  and  gas.  When 
reduced  to  sheets  it  is  made  into  gutters,  the  coverings  of  roofs, 
linings  for  troughs  and  reservoirs.  Sheet-iron  dipped  into  a 
bath  of  melted  lead  retains  a  coating  of  that  metal,  and  is  called 
leaded  iron.  Lead  enters  into  the  composition  of  type-metal, 
plumber's  solder,  pewter,  etc. 

LEAD   MONOXIDE. 
PbO 

Massicot  and  litharge,  of  which  the  formation  has  been  in- 
dicated, constitute  the  monoxide  of  lead. 

Massicot  is  a  yellow,  amorphous  powder.  Litharge  occurs  in 
reddish-yellow,  crystalline  scales.  It  is  rendered  crystalline  by 
the  fusion  and  cooling  through  which  it  passes.  It  is  sometimes 
met  with  in  the  form  of  rhombic  octahedra  (Mitscherlich). 

Oxide  of  lead  melts  at  a  red  heat ;  when  fused  it  absorbs 
oxygen,  which  it  again  gives  up  on  solidifying  (F.  Le  Blanc). 

It  cannot  be  melted  in  an  earthen  crucible  without  attacking 
and  sometimes  piercing  the  latter,  owing  to  the  formation  of  a 
very  fusible  silicate  of  lead. 

Lead  monoxide  is  easily  reduced  by  hydrogen,  charcoal,  and 
carbon  monoxide. 

It  is  very  slightly  soluble  in  water,  and  possesses  a  sufficiently 
Q  31 


362  ELEMENTS   OF   MODERN   CHEMISTRY. 

marked  alkaline  reaction  to  restore  the  blue  color  to  feebly 
reddened  litmus-paper. 

When  potassium  hydrate  or  ammonia  is  added  to  a  solution 
of  a  salt  of  lead,  a  white  precipitate,  which  is  a  hydrate  of  lead, 
is  formed.  This  hydrate  dissolves  in  an  excess  of  potassium 
hydrate ;  it  is  also  soluble  in  lime-water,  and  these  solutions 
are  precipitated  black  by  hydrogen  sulphide. 

Litharge  is  used  for  the  manufacture  of  lead  acetate  and 
white  lead.  It  gives  to  linseed  oil  drying  properties.  It  enters 
into  the  composition  of  various  plasters,  and  different  coloring 
matters  (Cassel's  yellow). 

LEAD  DIOXIDE. 

PbO2 

This  body  is  made  by  treating  minium,  or  intermediate  oxide 
of  lead,  with  dilute  nitric  acid.  A  brown  powder  remains  and 
must  be  washed  with  boiling  water.  This  is  dioxide  of  lead ; 
it  is  insoluble  in  water ;  it  is  readily  decomposed  by  heat,  losing 
half  of  its  oxygen  and  being  converted  into  monoxide.  It  is 
an  energetic  oxidizing  agent.  When  it  is  briskly  triturated 
with  a  small  quantity  of  sulphur,  the  latter  is  inflamed. 

If  lead  dioxide  be  introduced  into  a  test-tube  filled  with  sul- 
phurous acid  gas,  the  latter  is  immediately  absorbed  with  for- 
mation of  lead  sulphate. 

SO2  +  PbO2  =  PbSO4 

Hydrochloric  acid  poured  upon  lead  dioxide  determines  the 
formation  of  lead  chloride  and  the  disengagement  of  chlorine. 

PbO2  +  4HC1  ==  PbCl2  +  Cl2  +  2H20 

Lead  dioxide  unites  with  the  alkalies  forming  veritable  salts. 
Fremy  has  described  a  plumbate  of  potassium,  K2Pb03  -f 
3H20,  which  crystallizes  in  cubes,  and  which  is  formed  when 
dioxide  of  lead  is  gently  heated  with  a  very  concentrated  solu- 
tion of  potassium  hydrate  in  a  silver  crucible. 

PLUMBOSO-PLUMBIC  OXIDE   (RED  LEAD) 

This  oxide  is  prepared  by  heating  massicot  in  furnaces  to  a 
temperature  that  should  not  exceed  300°.  Under  these  con- 
ditions, the  monoxide  absorbs  oxygen  from  the  air,  and  is  con- 


LEAD    SULPHIDE.  363 

verted  into  a  beautiful  red  powder  known  as  minium  or  red  lead. 
The  product  obtained  by  heating  lead  carbonate  or  white  lead 
in  contact  with  the  air  is  called  orange  minium. 

Minium  is  a  combination  of  monoxide  and  dioxide  of  lead ; 
its  composition  is  variable,  according  to  the  length  of  time  it 
is  roasted.  It  ordinarily  corresponds  to  the  formula 

Pb304  =  2PbO.Pb02     (Jacquelain) 

Sometimes  it  contains  less  oxygen,  having  the  composition 

Pb405  =  3PbO.Pb02     (Mulder) 

Red  crystals  of  the  latter  composition  have  been  found  in 
the  fissures  of  a  minium  furnace. 

Minium  has  a  scarlet-red  color,  which  becomes  much  darker 
on  heating.  It  gives  up  oxygen  at  a  red  heat,  being  reduced 
to  monoxide.  If  red  lead  be  sprinkled  with  nitric  acid,  the 
color  disappears,  giving  place  to  a  brown.  The  nitric  acid 
removes  the  monoxide,  forming  nitrate,  and  leaves  the  brown 
dioxide. 

Minium  is  used  to  color  sealing-wax  and  wall-papers.  It  is 
employed  in  the  manufacture  of  flint  glass,  which  owes  its  fusi- 
bility, its  perfect  transparency  and  its  refractive  power,  to  sili- 
cate of  lead.  When  mixed  with  stannic  oxide,  minium  serves 
as  an  enamel  for  crockery-ware. 

A  mixture  of  red  lead  and  white  lead  with  a  small  quantity 
of  oil  is  employed  as  a  luting  for  steam-pipes,  and  as  a  cement. 

LEAD  SULPHIDE. 

PbS 

Galena  or  sulphide  of  lead  occurs  in  nature  in  beautiful 
cubical  crystals  of  a  bluish-gray  color  and  a  metallic  lustre ;  its 
density  is  7.58.  It  melts  at  a  red  heat.  When  heated  in  con- 
tact with  air,  it  is  converted  into  oxide  and  sulphate,  and  by  the 
reaction  of  an  excess  of  sulphide  upon  these  compounds  me- 
tallic lead  is  produced.  Hot  fuming  nitric  acid  converts  lead 
sulphide  into  sulphate.  Concentrated  and  boiling  hydrochloric 
acid  transforms  it  into  chloride  with  evolution  of  hydrogen 
sulphide. 

Galena  is  used  for  glazing  common  pottery.  A  broth  of 
powdered  galena  and  cow's  dung  mixed  with  water  is  applied 
to  the  surface  of  the  previously  well-dried  vessels. 


364  ELEMENTS   OP    MODERN    CHEMISTRY. 

This  sort  of  pottery  is  generally  baked  at  a  temperature  not 
very  high,  so  that  the  sulphide  of  lead,  the  oxidation  of  which 
is  prevented  by  the  cow's  dung,  melts  and  spreads  over  the  sur- 
face, forming  a  varnish  of  a  dark  color  when  cold.  Neverthe- 
less, a  small  quantity  of  oxide  is  always  formed  by  the  oxidation 
of  the  galena :  when  the  baking  takes  place  at  a  higher  temper- 
ature, this  oxide  forms  a  fusible  silicate,  which  covers  the 
pottery.  This  glazing  often  has  a  green  color,  due  to  the 
presence  of  oxide  of  copper,  and  is  attacked  by  vinegar  and 
other  acids,  which  dissolve  the  oxides  of  lead  and  copper. 
Hence  the  danger  in  the  use  of  ware  so  glazed  for  culinary 
purposes. 

LEAD  CHLORIDE. 

PbCP 

This  body  may  be  obtained  as  a  white,  crystalline  powder  by 
heating  litharge  with  hydrochloric  acid.  It  is  deposited  as  a 
dense,  white  precipitate  when  hydrochloric  acid  is  added  to  a 
concentrated  solution  of  acetate  or  nitrate  of  lead.  It  is  not 
very  soluble  in  water;  135  parts  of  water  at  12.5°,  or  33  parts 
of  boiling  water  being  required  to  dissolve  one  part  of  lead 
chloride.  It  may  be  obtained  crystallized  in  long  needles  by 
allowing  its  saturated  boiling  solution  to  cool.  Lead  chloride 
melts  below  a  red  heat,  and  on  cooling  solidifies  to  a  semi-trans- 
parent mass,  known  by  the  ancient  chemists  as  horn-lead. 

Mineral  yellow,  Turner  s  yellow,  and  CasseTs  yellow,  em- 
ployed in  painting,  are  oxychlorides  of  lead,  combinations  of 
lead  oxide  and  chloride  in  variable  proportions. 


LEAD   IODIDE. 
PbP 

When  a  solution  of  potassium  iodide  is  added  to  a  solution 
of  lead  acetate,  a  beautiful  yellow  precipitate  of  lead  iodide  is 
formed. 

This  body  melts  to  a  red-brown  liquid  at  a  high  temperature. 
It  requires  for  solution  1235  parts  of  cold,  or  194  parts  of 
boiling  water.  On  the  cooling  of  its  saturated,  boiling  solution, 
it  is  deposited  in  golden-yellow,  hexagonal  scales  having  a  mag- 
nificent lustre. 


LEAD    NITRATE — LEAD    SULPHATE.  365 

LEAD  NITRATE. 

Pb(NO3)2 

This  body  is  prepared  by  dissolving  litharge  in  dilute  nitric 
acid.  It  crystallizes  from  its  hot,  saturated  solution  in  anhy- 
drous, white,  regular  octahedra.  These  crystals  decrepitate 
when  they  are  heated ;  they  dissolve  in  7  i  times  their  weight 
of  cold  water,  and  in  a  much  less  quantity  of  boiling  water. 

At  a  red  heat  this  salt  is  decomposed  into  nitrogen  peroxide, 
oxygen,  and  lead  monoxide.  It  forms  various  basic  compounds 
with  lead  monoxide. 

When  one  molecule  of  the  nitrate  is  boiled  with  one  molecule 
of  the  monoxide,  and  the  filtered  solution  is  allowed  to  cool, 
a  crystalline  deposit  is  obtained,  which  is  a  dibasic  nitrate, 
Pb(N03)2  H-  Pb  -f  H20  (Pelouze).  This  salt  can  be  consid- 
ered as  derived  from  orthonitric  acid,  H3NO*  =  HNO3  -f- 
H20.  Indeed 

Pb(N03)2  +  PbO  +  H20  =  2^b  1  NO* 

This  basic  nitrate  of  lead  corresponds  to  the  basic  nitrate  of 
bismuth,  (page  351). 

Bi"'NO*  Pg  j  NO4 

Bismuth  subnitrate.  Lead  sulmitrate. 

When  a  solution  of  nitrate  of  lead  is  boiled  with  thin  sheet- 
lead,  the  latter  is  dissolved,  and  the  liquid  assumes  a  yellow 
color.  Under  these  conditions  soluble  basic  nitrites  of  lead  are 
formed.  On  cooling  the  filtered  liquid  deposits  yellow  crystals 
having  a  variable  composition.  By  a  prolonged  boiling  a  tetra- 
basic  nitrite,  Pb(N02)2  -f-  3PbO  -f  H20,  is  obtained.  The  so- 
lution of  the  latter,  decomposed  by  carbon  dioxide,  gives  the 
neutral  nitrite  Pb(NO2)2  -j-  H20,  crystallizing  in  long,  yellow 
prisms  (Peligot)  or  in  yellow  plates  (Chevreul). 

LEAD   SULPHATE. 

PbSO 

This  salt  is  found  crystallized  in  nature.  It  can  be  prepared 
by  double  decomposition  by  precipitating  the  solution  of  any 
soluble  lead  salt,  such  as  the  nitrate  or  acetate,  with  sulphuric 
acid  or  solution  of  a  sulphate.  It  is  a  white  powder,  insoluble 
in  water. 

31* 


366  ELEMENTS   OF   MODERN    CHEMISTRY. 

At  a  high  temperature,  lead  sulphate  melts  without  decom- 
position. Charcoal  reduces  it,  transforming  it  into  sulphide, 
metal,  or  oxide,  according  to  the  proportions  employed. 
Quickly  heated  with  an  excess  of  charcoal,  it  yields  sulphide. 

PbSO*  +  C2  =  2C02  +  PbS 

By  diminishing  the  proportion  of  charcoal,  a  residue  of 
metal,  or  even  of  oxide,  may  be  obtained. 

PbSO*  -f  C  =  CO2  +  SO2  +  Pb 
2PbS04  -f-  C  =  CO2  -f  2S02  +  2PbO 
Iron  and  zinc,  in  contact  with  lead  sulphate  suspended  in 
water,  cause  the  separation  of  metallic  lead. 

LEAD   CARBONATE. 

PbCO3 

Crystallized  lead  carbonate  is  found  in  nature.  The  salt 
may  be  obtained  artificially,  as  an  amorphous  white  powder,  by 
precipitating  a  soluble  lead  salt  by  an  excess  of  an  alkaline 
carbonate. 

A  hydrated,  and  sometimes  basic,  carbonate  of  lead  is  known 
as  ceruse  or  white  lead.  Its  composition  varies. 

PbCO3  +  H20  and  2PbC03  +  Pb(OH)2 

These  are  much  used  in  oil  painting.     White  lead  is  pre- 
pared by  several  methods,  the  oldest  of  which  is  called  the 
Dutch  process.     It  consists  in  exposing  sheets  of  lead  to  an 
atmosphere  charged  with  acetic  acid 
vapor  and  rich  in  carbonic  acid  gas. 
The   leaden  sheets  are   introduced 
into  glazed  earthen   pots,  A  (Fig. 
Ill),  containing  a  small  quantity  of 
vinegar.     The  lead  rests  upon  short 
projecting  arms,  B,  below  which  is 
placed    the    crude    vinegar.      The 
pots  are  covered  by  a  disk  of  lead, 
D,  which  incompletely  closes  them. 
FIG.  111.  They  are  then  arranged  in  rows  in 

large  chambers;   a  row   of  pots  is 

placed  on  a  bed  of  spent  tan  or  horse-manure ;  these  are  cov- 
ered with  planks,  upon  which  more  spent  tan  or  horse-manure 
is  placed,  and  then  another  layer  of  pots,  and  so  on.  The  fer- 


LEAD   CHROMATE.  367 

mentation  of  the  tan  or  manure  raises  the  temperature  to  30 
or  40°,  and  produces  carbonic  acid  gas.  On  the  other  hand, 
the  oxygen  of  the  air  intervenes,  causing  the  lead  to  be 
attacked  by  the  acetic  acid,  so  that  basic  acetate  of  lead  is 
formed  upon  the  surface  of  the  metal ;  but  this  salt  is  con- 
tinually decomposed  by  the  carbonic  acid  gas,  so  that  the  lead 
gradually  becomes  covered  with  a  layer  of  carbonate. 

Thenard  suggested  another  process  by  which  litharge  is  dis- 
solved in  a  solution  of  lead  acetate,  and  a  current  of  carbon 
dioxide  passed  through  the  solution  of  subacetate  so  formed. 
Lead  carbonate  is  precipitated  and  neutral  acetate  regenerated ; 
the  latter  is  then  again  transformed  into  basic  acetate.  The 
product  so  obtained  is  known  as  Clichy  white  lead. 

LEAD   CHROMATE. 

PbCrO* 

This  salt  exists  crystallized  in  nature,  constituting  the  red 
lead  of  Siberia.  It  is  prepared  by  double  decomposition 
between  solutions  of  potassium  chromate  and  lead  acetate ;  a 
yellow  precipitate  is  thus  obtained,  and  is  employed  in  painting 
under  the  name  chrome  yellow, 

Lead  chromate  melts  at  a  red  heat ;  at  a  white  heat  it  loses 
4  per  cent,  of  oxygen.  It  is  easily  reduced  by  charcoal  and 
hydrogen.  Insoluble  in  water,  it  dissolves  readily  in  solutions 
of  potassium  hydrate. 

Characters  of  Lead  Salts. — The  soluble  lead  salts  have  a 
sweetish  taste.  Black  precipitates  are  formed  in  their  solutions 
by  both  hydrogen  sulphide  and  ammonium  sulphide. 

Potassa  and  soda  yield  white  precipitates,  soluble  in  a  large 
excess  of  the  reagent.  Ammonia  gives  a  white  precipitate, 
insoluble  in  excess. 

Sulphuric  acid  forms  a  white  precipitate  even  in  the  most 
dilute  solutions  of  lead.  Hydrochloric  acid  forms  a  white 
precipitate  of  lead  chloride,  but  this  precipitate  is  not  produced 
in  dilute  solutions. 

Potassium  chromate  throws  down  a  yellow  precipitate,  soluble 
in  potassium  hydrate. 

When  heated  with  sodium  carbonate  upon  a  piece  of  charcoal 
in  the  reducing  flame  of  the  blow-pipe,  the  lead  salts  yield  a 
metallic  globule  which  when  cold  can  readily  be  flattened  out 
by  hammering. 


368 


ELEMENTS   OP   MODERN   CHEMISTRY. 


COPPER 

Cu(Cuprum)  =  63.5 

Natural  State. — Copper  is  found  in  the  native  state,  some- 
times crystallized  in  regular  octahedra,  sometimes  in  masses. 
It  is  also  found  as  cuprous  oxide,  Cu2O,  cupric  oxide,  CuO,  and 
cupric  carbonate,  CuCO3 ;  but  its  most  abundant  minerals  are 
cuprous  sulphide,  Cu2S  (Chalkosine),  and  a  double  sulphide 
of  copper  and  iron,  Cu2S.Fe2S3,  designated  as  copper  pyrites. 
Under  the  name  gray  copper  are  also  worked  various  minerals 
containing  cuprous  sulphide  combined  with  the  sulphides  of 
antimony  and  arsenic,  and  in  which  the  copper  is  sometimes 
replaced  by  iron,  zinc,  silver,  and  mercury. 

Treatment  of  Copper  Ores. — Copper  is  easily  extracted 
from  cuprous  oxide  and  cupric  carbonate.  These  ores  are 
melted  with  charcoal  in  suitable  furnaces,  and  the  metal  is  at 
once  obtained.  Copper  pyrites,  which  is  often  mixed  with 
cuprous  sulphide,  requires  a  more  complicated  treatment.  The 
iron  and  sulphur  must  be  eliminated,  and  for  this  reason  the 
ore  is  subjected  to  an  incomplete  roasting.  This  operation  is 
conducted  in  a  reverberatory  furnace  (Fig.  112).  The  flame 


FIG.  112. 


of  the  fire  sweeps  the  arched  vault  of  the  furnace  w.  The 
opening  of  the  chimney  is  at  C,  and  the  ore  is  fed  in  from  iron 
troughs  placed  above  the  furnace. 


COPPER.  369 

The  first  roasting  drives  out  part  of  the  sulphur,  and  the 
sulphides  of  iron  and  copper  are  partially  converted  into  oxides 
and  sulphates.  An  excess  of  sulphide  remains,  and  the  im- 
perfectly-roasted ore  is  fused  in  presence  of  silicious  materials. 
The  scoriae  formed  in  roasting  the  matt  (see  farther  on)  are 
generally  added,  and  sometimes  fluor  spar,  to  render  the  slag 
more  fusible.  This  operation  is  conducted  either  in  cupola-fur- 
naces or  in  reverberatory  furnaces  of  peculiar  construction.  In 
presence  of  the  unattacked  sulphide  of  iron,  the  cupric  oxide 
formed  during  the  roasting  is  converted  into  cupric  sulphide,  and 
oxide  of  iron  is  formed.  The  latter  unites  with  the  silica,  as 
does  also  the  oxide  produced  by  the  roasting,  both  being  reduced 
to  ferrous  oxide  by  the  reducing  gases  of  the  fire.  Ferrous  sili- 
cate is  thus  formed,  and  constitutes  a  very  fusible  slag,  below 
which  accumulates  the  sulphide  of  copper  containing  much  less 
sulphide  of  iron  than  the  original  pyrites.  This  product  is  the 
matt. 

The  sulphur,  which  was  thus  far  necessary  to  expel  the  iron, 
must  now  be  removed,  and  the  matt  is  broken  up  and  repeat- 
edly roasted,  by  which  the  remainder  of  the  iron  is  oxidized  and 
nearly  all  of  the  sulphur  expelled.  The  mineral  is  now  again 
melted  with  silicious  materials  and  the  scoriae  produced  in  re- 
fining black  copper,  and  rich  in  cupric  oxide,  are  added.  Ferrous 
silicate  separates  as  a  slag,  and  a  metallic  mass  containing  from 
90  to  94  per  cent,  of  copper,  still  alloyed  with  iron,  lead, 
arsenic,  sulphur,  etc.,  is  obtained.  This  product  constitutes 
black  copper. 

Refining  of  Black  Copper. — The  impure  metal  is  melted  in 
a  reverberatory  furnace ;  the  oxygen  of  the  air  transforms  the 
copper  into  oxide,  and  the  latter  is  gradually  reduced  by  the 
foreign  metals  and  the  sulphur  still  contained  in  the  mass  of 
copper ;  these  oxides  separate  in  the  form  of  scoriae  and  slags, 
which  are  removed.  The  liquid  copper  collects  in  a  cylin- 
drical cavity  in  the  furnace,  where  it  is  solidified  by  throwing 
cold  water  upon  the  surface  of  the  molten  metal ;  it  is  then 
removed  in  the  form  of  disks,  and  is  called  rosette  copper. 
The  copper  thus  obtained  is  brittle,  owing  that  property  to  the 
cupric  oxide  with  which  it  is  still  impregnated.  It  is  finally 
melted  under  a  layer  of  charcoal,  and  stirred  with  poles  of  green 
wood. 

Red,  ductile  copper  is  thus  obtained. 

At  Mansfeld,  in  Prussia,  a  copper  pyrites  is  worked  which 
Q* 


370  ELEMENTS   OF   MODERN   CHEMISTRY. 

is  disseminated  in  little  crystals  in  an  argillaceous  schist  impreg- 
nated with  bitumen.  After  a  series  of  roastings  and  smeltings, 
a  black  copper  is  obtained,  rich  enough  in  silver  to  permit  of 
the  advantageous  extraction  of  that  metal.  For  this  purpose 
the  method  called  liquation  is  employed.  The  argentiferous 
copper  is  melted  with  lead,  and  the  liquid  alloy  is  allowed  to 
cool  slowly.  Copper  solidifies  first,  alloyed  with  a  small  quan- 
tity of  lead,  while  the  remainder  of  the  lead,  retaining  nearly 
all  of  the  silver,  remains  liquid.  By  another  process  the  alloy 
of  lead  and  argentiferous  copper  is  made  into  disks,  D  (Fig.  113), 

and  these  are  reheated  very  slowly. 
As  soon  as  the  temperature  is  suf- 
ficiently high,  the  lead  melts  and 
runs  out,  carrying  with  it  all  of  the 
silver.  The  copper  remains  al- 
loyed with  a  small  quantity  of  lead. 
It  is  refined  by  melting  it  in  a  cu- 
pola-furnace under  the  blast  of  a 
FIG.  113.  tuyere.  The  lead  and  iron  and 

part  of  the  copper  are  oxidized, 

and  the  oxides  are  removed  as  scoriae.  Pure  copper  remains 
and  is  converted  into  rosette.  The  argentiferous  lead  is  sub- 
mitted to  cupellation,  as  already  described. 

Cement  copper  is  copper  precipitated  from  a  solution  of 
cupric  sulphate  by  metallic  iron.  It  is  very  pure. 

Properties  of  Copper. — This  metal  has  a  characteristic  red 
color  that  is  universally  known.  When  rubbed  with  the  hand 
it  exhales  a  peculiar,  disagreeable  odor.  By  fusion  it  crystal- 
lizes in  cubes,  but  it  may  be  deposited  by  electrolysis  in  reg- 
ular octahedra.  It  melts  towards  1100°,  and  maybe  volatilized 
by  the  heat  of  the  oxy-hydrogen  blow-pipe. 

Its  density  varies  from  8.85  to  8.95.  It  is  very  malleable, 
ductile,  and  tenacious. 

In  dry  air  it  is  unaltered  at  ordinary  temperatures,  but  it 
absorbs  oxygen  in  presence  of  moisture  and  carbonic  acid  gas. 
Green  spots  are  then  formed  upon  the  surface  of  the  metal, 
constituting  a  hydrocarbonate  of  copper ;  this  is  the  product 
ordinarily  called  verdigris. 

At  a  high  temperature  copper  absorbs  oxygen  with  avidity, 
being  converted  into  black,  cupric  oxide  if  the  oxygen  be  in 
excess ;  but  in  the  contrary  case,  red.  cuprous  oxide  is  formed. 
The  oxidation  is  favored  by  division  of  the  metal. 


CUPROUS   OXIDE.  371 

If  some  pulverulent  copper,  produced  by  the  decomposition 
of  copper  acetate,  be  thrown  upon  a  moderately  hot  tile  and  an 
incandescent  coal  be  approached  so  as  to  heat  one  point,  a  black 
spot  instantly  forms  there  and  rapidly  extends  throughout  the 
mass,  showing  the  progress  of  the  oxidation. 

In  presence  of  acids  or  ammonia,  copper  rapidly  absorbs 
oxygen  at  ordinary  temperatures. 

If  some  ammonia  and  copper-turnings  be  shaken  up  with  air 
in  a  glass-stoppered  bottle,  the  ammoniacal  liquid  becomes  blue; 
if  now  the  bottle  be  turned  upside-down  and  opened  under 
water,  the  latter  will  rise  in  the  bottle,  replacing  the  oxygen 
which  was  absorbed.  The  blue  liquid  contains  in  solution  am- 
moniacal oxide  of  copper  and  nitrite  of  copper  (Schonbein, 
Peligot). 

This  liquid  is  capable  of  dissolving  cotton  and  lint,  which 
are  almost  pure  cellulose  (Schweizer). 

When  heated  with  concentrated  sulphuric  acid,  copper  is 
converted  into  sulphate  with  disengagement  of  sulphurous 
acid  gas.  Nitric  acid,  even  dilute,  dissolves  it  readily,  forming 
cupric  nitrate  and  evolving  nitrogen  dioxide.  Boiling  hydro- 
chloric acid  attacks  it  slowly,  disengaging  hydrogen  and  forming 
cuprous  chloride. 

Uses  of  Copper. — Copper  is  much  employed  for  the  con- 
struction of  boilers,  alembics,  stills  and  worms,  and  for  kitchen 
utensils.  Sheet-copper  is  used  for  coating  the  bottoms  of  ships 
and  sometimes  for  roofing  houses.  This  metal  enters  into  the 
composition  of  the  more  important  alloys,  brass  (copper  and 
zinc),  bronze  (copper  and  tin),  German  silver  (copper,  zinc,  and 
nickel). 

CUPROUS   OXIDE. 
Cu2O 

This  oxide  is  found  in  nature,  sometimes  in  vitreous  masses, 
sometimes  in  beautiful,  red,  regular  octahedra. 

It  is  ordinarily  prepared  in  the  wet  way  by  boiling  a  solution 
of  acetate  of  copper  with  glucose  ;  a  bright-red,  crystalline  pow- 
der is  precipitated,  which  is  anhydrous  cuprous  oxide.  When 
heated  in  contact  with  air,  it  absorbs  oxygen  and  is  converted 
into  cupric  oxide. 

When  potassium  hydrate  is  added  to  a  solution  of  cuprous 
chloride,  a  yellow  precipitate  of  cuprous  hydrate  is  thrown 
down.  Cuprous  oxide  is  used  to  communicate  a  red  color  to  glass. 


372  ELEMENTS   OP   MODERN   CHEMISTRY. 

CUPRIC   OXIDE. 

CuO 

Two  processes  are  used  for  the  preparation  of  this  important 
body :  calcination  of  copper  in  the  air ;  calcination  of  cupric 
nitrate.  The  first  method  furnishes  a  granular,  compact,  black 
oxide ;  the  second,  a  fine,  deep-black  powder. 

Cupric  oxide  is  easily  reduced  by  both  hydrogen  and  char- 
coal, with  formation  of  either  water  or  carbon  dioxide. 

With  water  it  forms  a  hydrate,  Cu(OH)2  as  CuO.H20,  which 
precipitates  as  a  thick,  light-blue  magma,  when  potassium  hy- 
drate is  added  to  a  cupric  solution.  This  hydrate  is  converted 
into  brown,  anhydrous  oxide  by  boiling  with  water.  Cupric 
oxide  is  largely  used  in  the  laboratory  in  the  analysis  of  or- 
ganic substances.  It  is  used  in  the  arts  to  color  glass,  to  which 
it  imparts  a  green  color. 

SULPHIDES   OF   COPPER. 

Copper  forms  two  sulphides,  corresponding  to  the  oxides. 
Cuprous  sulphide,  Cu2S,  occurs  in  nature  in  fusible,  steel-gray 
crystals,  which  may  be  scratched  with  a  knife. 

Cupric  sulphide  CuS,  is  formed  in  the  wet  way  when  a 
solution  of  a  copper  salt  is  precipitated  by  hydrogen  sulphide. 
When  strongly  calcined,  it  loses  sulphur  and  is  reduced  to 
cuprous  sulphide. 

If  copper  filings  or  turnings  be  thrown  into  a  flask  containing 
boiling  sulphur,  a  brilliant  incandescence  takes  place  from  the 
union  of  the  two  elements. 

CHLORIDES   OF   COPPER. 

Cuprous  chloride,  Cu2Cl2,  is  prepared  by  boiling  copper- 
turnings  in  hydrochloric  acid  and  adding  small  quantities  of 
nitric  acid  from  time  to  time.  The  nitro-muriatic  acid  formed 
converts  the  copper  into  cupric  chloride,  which  is  reduced  by 
the  excess  of  copper  present.  A  brown  liquid  is  thus  obtained 
which,  by  continued  boiling,  becomes  almost  colorless.  On 
adding  water  to  this  liquid,  a  white,  crystalline  precipitate  of 
cuprous  chloride  is  deposited.  It  is  insoluble  in  water,  but  dis- 
solves in  aqueous  ammonia,  forming  a  liquid  which  remains 
colorless  when  kept  in  closed  vessels  in  presence  of  an  excess 


CUPRIC    SULPHATE.  373 

of  copper,  but  becomes  blue  on  exposure  to  the  air,  from  which 
it  absorbs  oxygen. 

Carbon  monoxide  is  perfectly  absorbed  by  a  solution  of 
cuprous  chloride  in  hydrochloric  acid  or  in  ammonia. 

Cupric  chloride,  CuCF,  is  obtained  by  dissolving  cupric  oxide 
in  hydrochloric  acid  or  in  aqua  regia.  A  green  solution  is 
formed,  which,  after  concentration,  deposits  beautiful  rhombic 
prisms  of  a  bluish-green  color,  containing  2  molecules  of  water 
of  crystallization. 

CUPRIC  SULPHATE. 

CuSO*  +  5H2O 

Preparation. — This  salt  is  commonly  called  blue  vitriol.  It 
is  a  product  of  many  industrial  operations,  such  as  roasting 
sulphurous  copper  ores,  and  the  decomposition  by  copper  of 
the  silver  sulphate  resulting  from  the  refining  of  gold, — that 
is,  the  treatment  of  silver  coin  containing  gold  with  sulphuric 
acid. 

Cupric  sulphate  produced  by  roasting  copper  ore  contains 
more  or  less  ferrous  sulphate.  The  two  salts  crystallize  together 
in  oblique  rhombic  prisms,  containing  7  molecules  of  water  of 
crystallization.  The  mixture  is  called  Salzburg  vitriol. 

Instead  of  copper  pyrites,  artificial  cupric  sulphide  may  be 
oxidized.  Old  copper  plates  are  moistened  and  sprinkled  with 
flowers  of  sulphur ;  they  are  then  heated  in  a  furnace,  and  the 
sulphide  of  copper  first  formed  is  converted  into  sulphate  by 
the  oxygen  of  the  air  drawn  into  the  furnace.  The  still  hot 
plates  are  plunged  into  water,  which  dissolves  the  layer  of  cupric 
sulphate,  and  the  same  operation  is  repeated  until  all  of  the 
metal  is  transformed  into  sulphate. 

The  simplest  process  consists  in  boiling  copper  turnings  and 
clippings  with  sulphuric  acid :  sulphurous  acid  gas  is  disen- 
gaged, and  cupric  sulphate  formed.  In  the  arts,  the  operation 
is  conducted  in  wooden  tanks  lined  with  lead  and  heated  by 
steam. 

Properties. — Cupric  sulphate  crystallizes  in  parallelopipedons 
belonging  to  the  type  of  the  dissymetric  prism.  These  crystals 
have  a  fine  blue  color,  and  contain  5  molecules  of  water.  When 
exposed  to  dry  air  they  effloresce  superficially :  heated  to  100°, 
they  lose  4  molecules  of  water,  disengaging  the  fifth  only  at 
243°.  The  anhydrous  salt  is  white.  At  a  high  heat,  cupric 

32 


3*74  ELEMENTS   OF   MODERN   CHEMISTRY. 

sulphate  is  decomposed  into  cupric  oxide,  sulphurous  oxide, 
and  oxygen. 

Cupric  sulphate  dissolves  in  4  parts  of  cold,  and  in  2  parts 
of  boiling  water,  and  the  concentrated  solution  has  a  pure  blue 
color.  It  is  insoluble  in  alcohol. 

When  an  excess  of  ammonia  is  added  to  a  solution  of  cupric 
sulphate,  a  beautiful,  dark-blue  liquid  is  obtained.  It  contains 
ammoniacal  cupric  sulphate,  CuSO4  -j-  4NH3  -f-  IPO,  which 
separates  in  dark-blue  crystals  when  alcohol  is  added  to  the 
aqueous  solution. 

There  are  several  basic  sulphates  of  copper  representing 
compounds  of  cupric  sulphate  and  cupric  hydrate.  One  of 
them  is  obtained  as  a  green  powder  when  a  solution  of  cupric 
sulphate  is  digested  with  cupric  hydrate.  The  bluish  precipi- 
tates obtained  by  incompletely  precipitating  solutions  of  cupric 
sulphate  with  potassium  hydrate  are  basic  sulphates. 

Uses. — Cupric  sulphate  is  employed  as  a  caustic  applicable 
to  diseases  of  the  eye.  In  the  arts,  it  is  used  in  the  prepara- 
tion of  blue  ashes,  a  mixture  of  calcium  sulphate  and  cupric 
hydrate,  made  by  decomposing  cupric  sulphate  with  milk  of 
lime. 

It  is  much  used  in  dyeing,  particularly  in  dyeing  black  on 
wool  and  cotton.  Its  solution  is  used  for  steeping  wheat. 
Large  quantities  of  sulphate  of  copper  are  employed  for  elec- 
trotyping. 

CARBONATES   OF    COPPER. 

When  cold  solutions  of  sodium  carbonate  and  cupric  sul- 
phate are  mixed,  a  bluish-green  precipitate  is  obtained,  and  at 
the  same  time  carbonic  acid  gas  is  disengaged.  The  precipi- 
tate becomes  green  when  washed  with  warm  water.  It  is 
known  as  mineral  green,  and  can  be  regarded  as  a  combina- 
tion of  one  molecule  of  cupric  carbonate  with  one  molecule  of 
cupric  hydrate.  It  contains 

CuCO3  +  Cu(OH)2 

A  similar  compound  exists  in  nature,  constituting  malachite. 
This  mineral  occurs  in  green  masses.  When  cut  and  polished, 
it  presents  veins  of  various  tints,  and  is  fashioned  into  orna- 
mental objects,  such  as  vases,  cups,  etc. 

Azurite  or  mountain  blue,  which  crystallizes  in  beautiful, 


CARBONATES   OF   COPPER.  3*75 

blue,  oblique  rhombic  prisms,  can  be  regarded  as  a  compound 
of  two  molecules  of  cupric  carbonate  with  one  of  the  hydrate. 

2CuC03  +  Cu(OH)2 

Debray  has  reproduced  azurite  artificially  by  leaving  calcium 
carbonate  for  a  long  time  in  contact  with  cupric  nitrate  in 
sealed  tubes. 

ALLOYS  OF  COPPER. 

Brass  is  an  alloy  of  copper  and  zinc,  ordinarily  containing  ^ 
zinc  and  f  copper.  It  often  contains  a  small  proportion  of  tin 
and  even  of  lead. 

Bronze  is  an  alloy  of  copper  and  tin  (see  table  of  alloys,  page 
237).  While  brass  is  malleable  and  ductile,  bronze  is  brittle 
when  it  has  been  slowly  cooled,  but  it  becomes  malleable  after 
tempering, — that  is,  when  it  is  heated  to  redness  and  then 
plunged  into  cold  water. 

German  silver  contains  25  per  cent,  of  zinc,  25  of  nickel, 
and  50  of  copper. 

Characters  of  Copper  Salts. — These  salts  are  blue  or  green. 
Their  solutions  are  precipitated  brown  by  hydrogen  sulphide 
and  ammonium  sulphide ;  an  excess  of  the  latter  reagent  will 
not  dissolve  the  precipitate. 

Potassium  hydrate  forms  a  dense,  light-blue  precipitate,  in- 
soluble in  excess.  Ammonia  first  forms  a  pale-blue  precipitate, 
which  is  then  dissolved  by  an  excess  of  the  reagent  with  a  rich 
sky-blue  color. 

Potassium  ferrocyanide  gives  a  chestnut-brown  precipitate 
even  in  very  dilute  cupric  solutions. 

An  apple-green  precipitate  of  cupric  arsenite  (Scheele's 
green)  is  formed  when  potassium  arsenite  is  added  to  cupric 
sulphate. 

A  bright  piece  of  iron  plunged  into  a  cupric  solution  in- 
stantly becomes  covered  with  a  deposit  of  metallic  copper. 


MERCURY. 

Hg  (Hydrargyrum)  =  200 

Natural  State  and  Extraction. — Mercury  occurs  native, 
and  especially  combined  with  sulphur,  mercuric  sulphide  or 
natural  cinnabar  being  its  principal  ore.  It  is  found  in  differ- 


376 


ELEMENTS    OF    MODERN    CHEMISTRY. 


ent  localities  in  Europe  and  America,  principally  at  Almaden, 
Spain;  Idria,  in  Illyria;  San  Jose,  in  California. 

The  treatment  of  the  ore  is  very  simple.  The  sulphide  is 
roasted  in  a  current  of  air  in  furnaces  of  peculiar  construction  : 
the  sulphur  is  oxidized,  and  passes  off  as  sulphur  dioxide,  the 
mercury  being  set  free.  The  metal  volatilizes  and  is  led,  to- 
gether with  the  gases  from  the  combustion,  either  into  con- 
densation-chambers, or  through  long  rows  of  little  cylindrical 
vessels,  where  the  mercury  condenses. 

Fig.  114  represents  the  furnaces  employed  at  Almaden, 
with  the  fireplace,  and  the  body,  AB,  charged  with  ore.  The 


FIG.  114. 

mercury-vapor  passes  by  o,  and  condenses  in  a  series  of  aludels 
entering  one  in  the  other,  and  arranged  upon  two  inclined  planes, 
ab,  be.  The  condensed  metal  runs  into  a  channel,  6,  from 
which  it  is  conducted  into  a  reservoir.  The  sulphurous  acid 
gas,  still  charged  with  vapor  of  mercury,  passes  into  a  chamber, 
C,  descending  to  the  floor,  where  it  is  cooled  by  contact  with  a 
trough  filled  with  water,  d.  In  this  chamber  the  condensation 
of  the  mercury-vapor  is  completed. 

Fig.  115  represents  the  several-storied  furnaces  aa,  &6,  cc, 
and  the  condensation-chambers  CC,  used  at  Idria. 

Cinnabar  may  also  be  reduced  by  iron  or  by  lime. 

The  metal  thus  extracted  is  purified  by  filtration  through 
ticking-cloth  or  chamois-skin.  It  is  ordinarily  transported  in 
forged  iron  bottles. 

The  mercury  of  commerce  is  nearly  always  alloyed  with  small 
quantities  of  other  metals,  such  as  lead,  tin,  copper,  and  bis- 


MERCURY. 


377 


muth.  In  this  state  its  surface  is  not  as  brilliant  as  when  pure, 
it  does  not  run  as  readily,  and  the  drops  are  drawn  out  to  a 
point.  They  are  said  to  form  tails.  It  may  be  purified  by  dis- 
tillation, an  operation  which  requires  certain  precautions,  and 
which  is  ordinarily  eifected  in  the  iron  bottles  which  serve  for 
the  transportation  of  the  metal. 

It  may  also  be  purified  by  digesting  it  for  several  days  with 
one-thirtieth  its  weight  of  commercial  nitric  acid  diluted  with 
its  own  weight  of  water ;  the  aqueous  liquid  is  then  decanted 
and  the  mercury  washed,  first  with  warm  water  acidulated  with 
nitric  acid,  then  with  pure  water,  after  which  it  can  be  dried. 
In  this  operation,  the  nitric  acid  removes  the  foreign  metals, 
more  oxidizable  than  the  mercury,  which  displace  the  latter 
metal  from  its  solution  in  the  nitric  acid. 


FIG.  115. 

Properties, — Mercury  is  liquid,  but  solidifies  at  — 40°.  The 
solid  metal  at  this  low  temperature  is  malleable,  and  has  a 
density  of  14.4.  The  density  of  liquid  mercury  is  13.595.  It 
boils  at  350°  of  an  air  thermometer.  Its  vapor  is  colorless, 
and  has  a  density  of  6.976. 

It  is  unaltered  by  contact  with  the  air  at  ordinary  tempera- 
tures, but  at  300°  it  slowly  absorbs  oxygen,  and  its  surface 
becomes  covered  with  a  red  powder,  which  is  mercuric  oxide, 
called  by  the  ancients  red  precipitate. 

Mercury  combines  with  chlorine,  bromine,  and  iodine  at  ordi- 
nary temperatures,  and  with  sulphur  by  the  aid  of  a  gentle  heat. 


378  ELEMENTS   OP   MODERN   CHEMISTRY. 

Hydrochloric  acid  does  not  attack  it.  Dilute  nitric  acid  dis- 
solves it  in  the  cold,  forming  mercurous  nitrate.  Hot  nitric 
acid  dissolves  it,  forming  mercuric  nitrate  and  evolving  red 
vapors. 

OXIDES   OF   MERCURY. 

Two  oxides  of  mercury  are  known,  mercurous  oxide,  Hg20, 
and  mercuric  oxide,  HgO. 

The  first  is  prepared  by  digesting  mercurous  chloride  (calo- 
mel) with  potassium  hydrate ;  a  black  powder  is  obtained  which 
is  very  unstable.  By  the  action  of  light,  or  by  a  temperature 
above  100°,  it  decomposes  into  mercuric  oxide  and  mercury. 

Mercuric  Oxide,  HgO,  can  be  obtained  by  either  the  dry  or 
wet  method.  The  first  consists  in  decomposing  mercuric  nitrate 
by  heat;  the  salt  is  gradually  heated  in  a  flask  on  a  sand- 
bath  until  red  vapors  cease  to  be  disengaged. 

The  oxide  thus  prepared  is  an  orange-red,  granular,  and 
crystalline  powder. 

Mercuric  oxide  is  prepared  in  the  wet  way  by  decomposing 
a  solution  of  mercuric  chloride  by  potassium  hydrate.  A 
yellow  precipitate  of  anhydrous  mercuric  oxide  is  obtained. 

When  mercuric  oxide  is  heated,  it  assumes  a  dark-red  color 
and  decomposes,  if  the  temperature  be  above  400°,  into  oxygen 
and  mercury.  It  yields  its  oxygen  to  many  bodies,  such  as 
charcoal,  sulphur,  and  phosphorus,  which  it  oxidizes  energet- 
ically. When  heated  with  sulphur,  it  produces  an  explosion. 
In  these  reactions  the  finely-divided  yellow  oxide  is  more  active 
than  the  red  oxide. 

MERCURIC  SULPHIDE. 

HgS 

This  is  the  cinnabar  generally  fotfnd  in  nature  in  compact 
masses,  sometimes  in  transparent,  red,  hexagonal  prisms  or 
rhombohedra.  It  is  manufactured  by  directly  combining  sul- 
phur and  mercury.  The  combination  takes  place  when  the 
bodies  are  triturated  together  in  the  cold,  in  the  proportion  of 
100  parts  of  mercury  and  18  parts  of  sulphur.  A  black  mass 
is  thus  obtained  which  is  sublimed  in  iron  vessels. 

Cinnabar  prepared  by  sublimation  occurs  in  dark-red  masses, 
having  a  fibrous  and  crystalline  structure.  Its  density  is  8.124. 
At  a  high  temperature,  it  volatilizes  without  melting.  When 


MERCUROUS   CHLORIDE.  3*79 

heated  in  the  air,  it  burns  with  a  blue  flame,  yielding  sulphur- 
ous acid  gas  and  metallic  mercury.  It  is  decomposed  by  hydro- 
gen, charcoal,  and  most  of  the  metals.  Boiling  sulphuric  acid 
decomposes  it  with  formation  of  sulphurous  acid  gas  and  sul- 
phate of  mercury.  Nitric  acid  scarcely  attacks  it,  even  when 
boiling. 

Vermillion  is  a  finely-divided  mercuric  sulphide  having  a 
rich  scarlet  color.  It  is  prepared  by  triturating  for  several 
hours  in  a  mortar,  300  parts  of  mercury  and  114  parts  of 
flowers  of  sulphur,  and  adding  to  the  black  sulphide  thus  ob- 
tained 75  parts  of  potassa  and  400  parts  of  water.  The  mixture 
is  maintained  at  a  temperature  of  about  45°,  being  continually 
triturated  with  a  pestle.  As  soon  as  the  powder  has  acquired 
a  fine  scarlet  color,  it  is  rapidly  washed  with  hot  water  and 
dried.  It  is  employed  in  painting  and  also  to  color  sealing- 
wax. 


MERCUROUS  CHLORIDE,  OR  CALOMEL. 
Hg«Cl> 

Mercurous  chloride  is  largely  used  in  medicine  under  the 
name  calomel  or  mild  chloride  of  mercury. 

Preparation. — An  intimate  mixture  of  mercurous  sulphate 
and  sodium  chloride  is  heated  in  a  capacious  glass  matrass  on 
a  sand-bath.  The  mercurous  chloride,  formed  by  double  decom- 
position, sublimes. 

Hg2S04  +.2NaCl  —  Hg2Cl2  +  Na'SO4 

It  is  thus  obtained  in  compact,  crystalline  masses.  When 
it  is  strongly  heated  and  its  vapor  passed  into  large  stoneware 
vessels  filled  with  steam,  it  condenses  in  an  impalpable  powder, 
in  which  form  it  is  used  by  preference  in  medicine. 

Calomel  may  also  be  prepared  in  the  wet  way  by  adding 
hydrochloric  acid,  or  a  solution  of  sodium  chloride,  to  a  solu- 
tion of  mercurous  nitrate.  A  white,  curdy  precipitate  is 
obtained  which  is  washed  and  dried. 

Properties. — Prepared  in  the  dry  way  calomel  occurs  as 
dense,  fibrous,  crystalline  and  slightly  transparent  masses,  one 
side  of  which  is  smooth,  the  other  presenting  the  sharp  points 
of  the  crystals.  When  exposed  to  light,  it  becomes  yellow  and 
even  gray  in  time,  being  partially  decomposed.  Its  density  is 


380  ELEMENTS   OP   MODERN   CHEMISTRY. 

7.1 7.  The  density  of  its  vapor  is  8.35.  It  melts  and  vola- 
tilizes at  the  same  temperature.  When  slowly  sublimed,  it 
crystallizes  in  square  prisms.  It  is  insoluble  in  water. 

A  solution  of  potassium  iodide  agitated  with  calomel  con- 
verts it  into  a  green  powder  of  mercurous  iodide.  If  an  excess 
of  potassium  iodide  be  employed,  the  green  powder  disappears 
and  is  replaced  by  a  gray  precipitate  of  metallic  mercury,  the 
mercurous  iodide  at  first  formed  being  decomposed  into  mercury 
and  mercuric  iodide,  which  dissolves  in  the  potassium  iodide. 

An  analogous  reaction  takes  place  with  the  alkaline  chlorides 
by  the  aid  of  heat,  the  mercurous  chloride  breaking  up  into 
mercuric  chloride  which  dissolves,  and  metallic  mercury  which 
is  deposited. 

MERCURIC    CHLORIDE,   OR    CORROSIVE    SUBLI- 
MATE. 

HgCl2 

Preparation. — This  body  is  obtained  by  double  decomposi- 
tion, by  heating  a  mixture  of  mercuric  sulphate  and  sodium 
chloride  on  a  sand-bath.  The  mercuric  chloride  condenses  in 
the  upper  part  of  the  matrasses  which  are  imbedded  up  to  the 
neck  in  the  sand. 

HgSO4  +  2NaCl  —  Na2S04  -f  HgCP 

Towards  the  close  of  the  operation  the  heat  is  increased  in 
order  to  agglomerate  the  sublimate  by  a  partial  fusion. 

Another  process  consists  in  passing  chlorine  into  heated 
mercury ;  the  combination  takes  place  with  the  production  of 
luminous  heat. 

Properties. — Mercuric  chloride  prepared  by  the  dry  method 
occurs  in  compact,  white,  crystalline  and  friable  masses,  having 
a  density  of  6.5.  It  is  an  energetic  poison.  It  melts  at  about 
265°,  and  boils  towards  295°.  The  density  of  its  vapor  is 
9.42.  By  sublimation  it  may  be  obtained  crystallized  in  rec- 
tangular octahedra. 

It  is  soluble  in  19  parts  of  cold  water,  also  in  alcohol  and  ether. 
It  is  deposited  from  its  hot,  saturated,  aqueous  solution  in 
long  prisms,  belonging  to  the  type  of  the  right  rhombic  prism. 
The  crystals  are  anhydrous. 

The  aqueous  solution  of  mercuric  chloride  produces  a  white 
precipitate  in  a  solution  of  albumen  of  white  of  egg.  This 


MERCUROUS    IODIDE — MERCURIC    IODIDE.  381 

precipitate  is  a  combination  of  mercuric  chloride  and  albumen. 
Albumen  is  thus  the  antidote  to  corrosive  sublimate. 

When  a  slight  excess  of  ammonia  is  added  to  a  solution  of 
corrosive  sublimate,  a  white  deposit  is  formed,  known  as  white 
precipitate,  of  which  the  composition  is  expressed  by  the 
formula  HgH2NCl. 

HgCP  +  2NH3  =  NH4C1  +  HgH2NCl 

It  may  be  regarded  as  the  chloride  of  mercury-ammonium, 
that  is,  ammonium  chloride  in  which  2  atoms  of  hydrogen  are 
replaced  by  one  atom  of  the  diatomic  metal  mercury. 

Hg") 

HgH2NCl  =   H    [  NCI 
H    ) 

Corrosive  sublimate  forms  crystallizable  double  combinations 
with  the  alkaline  chlorides  and  with  ammonium  chloride. 

MERCUROUS  IODIDE. 
Hg»I» 

This  compound  is  ordinarily  prepared  by  directly  combining 
mercury  and  iodine.  100  parts  of  mercury  and  63.5  parts  of 
iodine  are  triturated  with  a  small  quantity  of  alcohol,  until  the 
whole  is  converted  into  a  green  powder,  which  is  then  washed 
with  boiling  alcohol  and  dried. 

It  may  also  be  prepared  by  double  decomposition  by  precipi- 
tating a  solution  of  mercurous  nitrate  with  potassium  iodide, 
or  by  the  reaction  of  the  latter  body  upon  calomel. 

Mercurous  iodide  is  not  a  stable  compound.  It  is  decom- 
posed by  light.  Heat  breaks  it  up  into  mercury  and  mercuric 
iodide,  and  the  same  decomposition  is  effected  by  potassium 
iodide  and  the  alkaline  chlorides. 

MERCURIC   IODIDE. 

Hgl2 

Mercuric  iodide  is  prepared  by  pouring  a  solution  of  100 
parts  of  potassium  iodide  into  a  solution  of  80  parts  of  corro- 
sive sublimate.  A  beautiful  scarlet-red  precipitate  of  mercuric 
iodide  is  thrown  down. 

It  is  necessary  that  the  bodies  be  employed  in  the  propor- 


382  ELEMENTS   OF   MODERN   CHEMISTRY. 

tions  indicated ;  an  excess  of  potassium  iodide  would  dissolve 
the  mercuric  iodide  first  precipitated. 

Mercuric  iodide  is  almost  insoluble  in  water ;  it  is  slightly 
soluble  in  boiling  alcohol,  which  deposits  it  on  cooling  in  small 
red  octahedral  crystals. 

If  mercuric  iodide  be  heated  in  a  small  glass  retort,  it  melts 
to  a  dark-yellow  liquid  which  solidifies  on  cooling  to  a  yellow 
mass.  At  a  higher  temperature  the  liquid  boils  and  its  vapor 
condenses  in  a  dark-yellow  liquid  which  solidifies  to  a  yellow 
mass ;  at  the  same  time,  right  rhombic  prisms  of  a  yellow  color 
sublime.  If  these  be  rubbed  with  a  glass  rod  or  other  hard 
body  they  instantly  become  red,  first  at  the  point  of  contact, 
then  throughout  the  entire  mass. 

These  two  forms  of  mercuric  iodide  constitute  one  of  the 
most  curious  examples  of  dimorphism. 

Mercuric  iodide  forms  a  combination  with  potassium  iodide 
which  is  soluble  in  water.  A  solution  of  this  iodo-hydrargyrate 
of  potassium  is  not  precipitated  by  potassium  hydrate,  but  the 
liquid  rendered  alkaline  by  the  latter  reagent  is  a  very  sensi- 
tive test  for  ammonia  (Nesslers  test),  with  which  it  gives  a  pre- 
cipitate or  a  brown  cloud  more  or  less  intense,  according  to  the 
quantity  of  ammonia  present. 

NITRATES   OF   MERCURY. 

Neutral  mercurous  nitrate  (Hg2)"(N03)2  -f  2H20,  is  ob- 
tained by  the  action  of  an  excess  of  cold,  dilute  nitric  acid  upon 
metallic  mercury.  After  some  time,  short  colorless  prisms  are 
formed  in  the  liquid,  constituting  the  neutral  salt.  The  latter 
is  readily  soluble  in  water  charged  with  nitric  acid. 

When  mercury  is  attacked  by  an  excess  of  boiling  nitric 
acid  and  the  solution  is  evaporated,  voluminous  crystals  of  a 
basic  mercuric  nitrate  separate,  Hg(N03)2.HgO  -j-  2H2O. 

The  syrupy  liquid  from  which  these  crystals  are  deposited, 
contains  neutral  mercuric  nitrate. 

Hg(N03)2  +  8H20 

This  salt  is  deposited  in  large,  colorless,  rhombic  tables  when 
the  syrupy  solution  is  cooled  to  — 15°. 

A  large  quantity  of  cold  water  decomposes  this  nitrate  into 
nitric  acid  which  dissolves,  and  a  basic  salt,  Hg(N03)2.2HgO 
-f-  H20,  forming  a  yellow  powder. 


SULPHATES   OF   MERCURY.  383 


SULPHATES  OF  MERCURY. 

There  is  a  mercurous  sulphate,  (Hg2)"S04,  and  a  mercuric 
sulphate,  Hg"S04. 

The  first  is  obtained  by  heating  equal  parts  of  mercury  and 
sulphuric  acid,  arresting  the  operation  when  two-thirds  of  the 
mercury  are  converted  into  a  white,  crystalline  powder.  Mer- 
curous sulphate  is  but  slightly  soluble  in  cold  water. 

To  prepare  mercuric  sulphate,  1  part  of  mercury  and  1J 
parts  of  sulphuric  acid  are  heated  to  complete  desiccation  on  a 
sand-bath. 

Hg  +  2H2S04  ==  2H20  +  HgSO4  +  SO2 

It  is  well  to  add  a  small  quantity  of  nitric  acid  before  drying. 

Mercuric  sulphate  is  an  anhydrous,  white  powder.  It  decom- 
poses at  a  red  heat  into  metallic  mercury,  sulphurous  acid  gas, 
and  oxygen.  Charcoal  reduces  it  readily,  equal  volumes  of 
carbon  dioxide  and  sulphur  dioxide  being  disengaged. 

Mercuric  sulphate  is  slightly  soluble  in  water :  a  large  quan- 
tity of  cold  water  converts  it  into  a  yellow,  basic  salt,  HgSO4. 
2HgO,  known  as  turpeth  mineral. 

Characters  of  Mercurous  Salts. — Their  solutions  are  pre- 
cipitated black  by  hydrogen  sulphide,  and  also  by  potassium 
hydrate  and  ammonia.  Hydrochloric  acid  gives  a  white  pre- 
cipitate which  is  blackened  by  ammonia.  Potassium  iodide 
forms  a  green  precipitate  of  mercurous  iodide,  converted  by 
an  excess  of  the  reagent  into  mercuric  iodide  which  dissolves, 
and  gray  metallic  mercury. 

Characters  of  Mercuric  Salts. — Solutions  of  mercuric  salts 
are  precipitated  black  by  an  excess  of  hydrogen  sulphide,  and 
by  ammonium  sulphide. 

Potassium  hydrate  forms  a  yellow  precipitate,  insoluble  in 
excess. 

Ammonia  yields  a  white  precipitate  in  solutions  of  corrosive 
sublimate. 

Hydrochloric  acid  does  not  precipitate  the  mercuric  salts. 

Iron,  zinc,  and  copper  precipitate  metallic  mercury  from 
both  mercurous  and  mercuric  solutions.  A  slip  of  copper 
dipped  into  such  solutions  becomes  covered  with  a  gray  coating 
which  acquires  brilliancy  by  rubbing. 

Heated  with  lime  in  a  glass  tube,  all  of  the  mercury  com- 
pounds yield  metallic  mercury  which  sublimes  in  small  globules, 


384 


ELEMENTS   OF   MODERN   CHEMISTRY. 


easy  to  recognize  under  the  microscope,  and  which  can  be  char- 
acterized by  the  addition  of  iodine,  the  vapor  of  which  converts 
the  metallic  globules  into  yellow  or  red  mercuric  iodide. 


SILVER 

Ag(Argentum)  =  108 

Natural  State. — Silver  is  found  native  and  in  combination 
in  many  minerals.  Among  these  are  the  sulphide,  the  sulph- 
antimonides  and  sulpharsenides,  the  antimonide,  chloride,  bro- 
mide, iodide,  selenide,  telluride,  and  lastly  an  amalgam  of 
silver.  It  is  found  in  small  proportions  in  many  galenas  and 
copper  pyrites. 

Treatment  of  Silver  Ores. — The  silver  is  extracted  from 
galena  by  first  reducing  the  lead,  and  then  submitting  the 
argentiferous  lead  obtained  to  cupellation  (page  359). 

Silver  ores  free  from  lead  are  treated  by  a  peculiar  process 
called  amalgamation ,  since  it  is  based  upon  the  employment 
of  metallic  mercury  which  dissolves  silver ;  the  amalgam  of 
silver  formed  is  decomposed  by  heat. 

Several  processes  are  employed  for  the  chlorination  and 
amalgamation  of  silver. 

Freiberg  Amalgamation  Process. — The  Freiberg  silver  ore 
is  poor,  containing  only  two  or  three  thousandths  of  silver  in 
the  form  of  sulphide,  disseminated 
through  iron  and  copper  pyrites. 
The  ore  is  pulverized,  mixed  with 
one-tenth  its  weight  of  common 
salt,  and  roasted  in  a  reverberatory 
furnace.  The  sulphides  are  oxi- 
dized, with  disengagement  of  sul- 
phurous acid  gas  and  formation  of 
sulphates.  The  latter  react  upon  the 
sodium  chloride,  forming  sodium 
sulphate  and  metallic  chlorides :  all 
of  the  silver  is  thus  converted  into 
chloride.  The  product  of  the  roast- 
ing is  reduced  to  powder,  washed, 
and  introduced,  together  with  water  and  scrap-iron,  into  amal- 
gamation barrels,  which  are  rotated  by  water-power  (Fig.  116). 
When  the  mixture  has  become  homogeneous,  mercury  is  added 


FIG.  116. 


SILVER. 


385 


FIG.  117. 


and  dissolves  the  silver  set  free  by  the  action  of  the  iron  upon 
the  silver  chloride ;  it  also  dissolves  a  small  quantity  of  copper 
formed  by  the  reduction  of  cuprous  chloride  present.  After 
the  barrels  have  been  rotated  for  some  hours,  the  amalgam  is 
collected  and  compressed  in  canvas  bags,  through  which  the 
excess  of  mercury,  alloyed  with  a  very  small  quantity  of 
foreign  metals,  passes,  while  a  pasty  .  f. 

amalgam  of  silver  and  copper  remains 
in  the  bags.  This  amalgam  is  put  into 
iron  cups,  bb  (Fig.  117),  set  upon  an 
iron  rod  on  a  tripod  base,  a,  standing  in 
a  vessel  of  water.  The  whole  is  cov- 
ered with  a  bell-shaped  iron  hood  which 
dips  into  the  water,  and  the  upper  part 
of  which  is  surrounded  by  burning 
coals.  The  mercury  volatilizes  and 
condenses  in  the  cold  water,  and  an 
alloy  of  silver  and  copper,  containing 
about  28  per  cent,  of  the  latter  metal, 
as  well  as  small  quantities  of  lead, 
antimony,  etc.,  remains  in  the  cups. 
It  is  purified  either  by  cupellation  or  by  refining. 

Cupellation  consists  in  melting  the  impure  silver  with  lead, 
as  has  been  already  described.  In  refining,  the  silver  is  melted 
in  a  hemispherical  iron  vessel  lined  with  a  thick  layer  of  marl 
and  wood  ashes.  It  is  a  porous  cupel,  which  absorbs  the  oxides 
formed  by  the  action  of  the  air  upon  the  lead  and  copper 
alloyed  with  the  silver ;  the  latter  remains  in  the  cupel  at  the 
close  of  the  operation  in  a  pure  state. 

Mexican  Amalgamation  Process. — American  silver  ore  con- 
sists of  sulpharsenide  and  sulphantimonide  of  silver,  mixed  with 
silver  chloride  and  native  silver,  the  whole  being  disseminated 
in  silica,  calcium  carbonate,  and  ferric  oxide.  In  Mexico,  the 
following  primitive  process  is  still  used.  The  finely-pulverized 
ore  is  mixed  with  two  per  cent,  of  common  salt  and  thrown 
into  circular  areas  paved  with  flag-stones,  where  it  is  rendered 
homogeneous  by  being  trodden  for  several  hours  by  mules. 
About  one  per  cent,  of  copper  pyrites  which  has  been  roasted 
in  the  air  and  contains  cupric  sulphate  is  then  added.  The 
latter  salt  reacts  with  the  sodium  chloride,  forming  sodium  sul- 
phate and  cupric  chloride,  which  latter  decomposes  the  silver 
sulphide,  forming  silver  chloride  and  cupric  sulphide.  Mer- 
B  33 


386  ELEMENTS    OP    MODERN    CHEMISTRY. 

cury  is  then  added  and  reduces  the  silver  chloride,  with  for- 
mation of  chloride  of  mercury  and  metallic  silver.  During  the 
whole  time  the  mass  is  continually  trodden  by  the  mules,  and 
the  mercury  comes  in  contact  with  the  disseminated  silver :  the 
amalgam  formed  solidifies  in  about  a  fortnight.  A  second  and 
finally  a  third  addition  of  mercury  is  then  made  until  7  or  8 
parts  of  that  metal  have  been  employed  for  one  part  of  silver 
to  be  extracted.  After  a  few  months,  the  operation  is  termi- 
nated, and  the  mass  is  washed  with  large  quantities  of  water  to 
remove  the  earthy  and  salty  matters.  The  amalgam  remains, 
and  is  heated  in  order  to  extract  the  silver. 

American  Process. — The  above  method  of  extraction  is  too 
slow  to  be  employed  for  the  vast  quantities  of  silver  ore  that 
are  mined  on  the  Pacific  Slope.  The  ore  is  there  crushed  and 
roasted  with  sodium  chloride  and  a  small  proportion  of  cupric 
sulphate,  in  furnaces  of  a  peculiar  construction.  By  this  means 
all  of  the  silver  is  converted  into  chloride.  The  mass  is  made 
into  a  pulp  with  water  and  agitated  with  mercury  in  large  tanks 
or  vats.  The  silver  chloride  is  reduced  as  before,  and  the 
amalgam  obtained  is  first  squeezed  out  and  afterwards  heated 
in  iron  retorts  to  expel  the  mercury. 

Properties. — Silver  is  the  whitest  and  most  brilliant  of  all 
the  ordinary  metals.  Next  to  gold,  it  is  the  most  malleable 
and  the  most  ductile.  Its  density  is  10.5. 

It  melts  towards  1000°,  and  when  fused  has  the  curious 
property  of  dissolving  oxygen,  of  which  it  absorbs  22  times  its 
volume.  On  solidifying,  it  again  disengages  the  gas  ;  this  phe- 
nomenon, which  occasionally  causes  the  projection  of  portions 
of  silver,  is  called  spitting.  Silver  volatilizes  at  the  high  tem- 
perature of  the  oxyhydrogen  blow-pipe. 

It  is  unaltered  by  the  air.  It  absorbs  ozone,  being  converted 
into  the  dioxide  Ag202.  It  combines  with  hydrogen  dioxide, 
forming  argentous  and  argentic  hydrates  (Weltzien). 

It  decomposes  concentrated  solution  of  hydriodic  acid,  dis- 
engaging hydrogen  and  forming  silver  iodide  (Deville).  Hy- 
drochloric acid  only  attacks  it  superficially.  Hydrogen  sulphide 
blackens  it,  forming  a  pellicle  of  silver  sulphide.  Its  best  sol- 
vent is  nitric  acid  which  attacks  it  in  the  cold,  yielding  silver 
nitrate  and  disengaging  red  vapors. 

The  alkalies  have  no  action  upon  silver;  for  this  reason,  silver 
vessels  are  used  for  fusing  potassium  hydrate  and  concentrating 
its  solution. 


SILVER  SULPHIDE — SILVER  CHLORIDE.  387 


SILVER  OXIDE. 

Ag'O 

The  only  important  oxide  of  silver  is  the  monoxide,  which 
is  precipitated  in  the  anhydrous  state  when  potassium  hydrate, 
free  from  chloride,  is  added  to  a  solution  of  silver  nitrate. 

It  forms  an  olive-brown,  flocculent  deposit  which  yields  a 
brown  powder  on  drying. 

Silver  oxide  is  readily  decomposed  by  heat  into  silver  and 
oxygen.  It  is  reduced  by  hydrogen  at  a  temperature  below 
100°.  When  recently  precipitated,  it  is  slightly  soluble  in 
water.  It  is  an  energetic  base,  perfectly  neutralizing  the  acids, 
and  displacing  cupric  oxide  from  the  cupric  salts. 

When  oxide  of  silver  is  digested  with  ammonia  it  is  con- 
verted into  a  very  explosive,  black  powder,  known  as  fulmi- 
nating silver.  Its  composition  is  not  yet  well  known. 

SILVER  SULPHIDE. 

Ag2S 

To  the  oxide  of  silver  corresponds  the  sulphide  Ag2S,  which 
occurs  native,  crystallized  in  regular  octahedra,  ordinarily  mod- 
ified by  facettes.  It  is  soft  and  can  be  scratched  by  the  finger- 
nail. Silver  and  sulphur  also  combine  readily  by  the  aid  of 
heat. 

SILVER   CHLORIDE. 

AgCl 

This  body  is  found  native  and  is  known  to  mineralogists  as 
horn-silver.  It  is  sometimes  found  crystallized  in  cubes  and 
octahedra.  It  is  formed  directly  when  silver  is  heated  in  chlo- 
rine gas,  and  is  prepared  by  double  decomposition  by  adding 
hydrochloric  acid  or  a  solution  of  sodium  chloride  to  solution 
of  nitrate  of  silver.  A  white,  curdy  precipitate  is  thus  obtained, 
which  assumes  a  violet  tint  when  exposed  to  the  action  of  light. 
The  change  of  color  is  due  to  partial  decomposition. 

Silver  chloride  melts  at  about  260°,  and  solidifies  on  cooling 
to  a  gray,  horn-like  mass  that  can  be  cut  with  a  knife. 

If  recently  precipitated  and  moist  silver  chloride  be  placed 
upon  a  sheet  of  zinc,  in  a  short  time  a  dark  color  will  appear 
on  the  borders  of  the  chloride,  and  the  whole  of  that  body  will 


388  ELEMENTS   OF   MODERN   CHEMISTRY. 

soon  be  converted  into  a  dark-gray  powder  of  finely-divided 
silver.  Zinc  chloride  is  at  the  same  time  formed. 

This  reaction  takes  place  much  more  rapidly  if  the  silver 
chloride  be  moistened  with  hydrochloric  acid.  In  this  case 
the  reduction  is  effected  by  nascent  hydrogen  produced  by  the 
action  of  the  hydrochloric  acid  on  the  zinc. 

When  silver  chloride  is  fused  with  the  alkaline  hydrates  or 
carbonates,  it  is  reduced  to  metallic  silver :  oxygen  is  disen- 
gaged, and  an  alkaline  chloride  is  formed. 

Recently-precipitated  silver  chloride  dissolves  readily  in  aque- 
ous ammonia.  When  dry,  it  absorbs  ammonia  gas  abundantly, 
and  Faraday  employed  this  compound  for  the  preparation  of 
liquid  ammonia. 

Silver  chloride  dissolves  also  in  solutions  of  the  alkaline 
hyposulphites. 

SILVER  IODIDE. 
Agl 

Silver  iodide  is  obtained  as  a  yellow  precipitate  by  adding 
potassium  iodide  to  a  solution  of  silver  nitrate.  It  blackens 
on  exposure  to  light.  It  is  but  very  slightly  soluble  in  ammo- 
nia, a  property  which  distinguishes  it  from  silver  chloride. 

SILVER  NITRATE. 
AgNO» 

This  salt  is  prepared  by  dissolving  silver  in  nitric  acid.  If 
the  metal  be  pure,  a  colorless  solution  is  obtained  which  after 
concentration  and  cooling  deposits  large,  colorless  tables  of  an- 
hydrous silver  nitrate.  If  silver  coin  be  employed,  the  solution 
will  be  blue,  containing,  independently  of  silver  nitrate,  cupric 
nitrate.  The  latter  may  be  removed  by  evaporating  the  residue 
to  dryness  and  carefully  heating  it,  so  that  the  salt  may  remain 
fused  for  some  time.  The  cupric  nitrate  is  decomposed,  while 
the  silver  nitrate  remains  mixed  with  cupric  oxide,  from  which 
it  may  be  freed  by  solution  and  filtration. 

Fused  silver  nitrate  constitutes  lunar  caustic. 

This  salt  dissolves  in  its  own  weight  of  cold,  and  in  half  its 
weight  of  boiling  water.  The  solution  is  neutral  to  test-paper. 
When  exposed  to  the  air,  it  blackens,  as  do  also  the  crystals 
and  the  fused  salt,  by  reason  of  a  partial  reduction  due  to  the 
organic  matters  suspended  in  the  air. 


ASSAYING   OF    SILVER.  389 

It  blackens  the  skin  from  a  similar  cause. 

Hydrogen  slowly  reduces  the  solution  of  silver  nitrate  with 
deposition  of  metallic  silver  (Beketoff). 

Characters  of  Silver  Salts. — Solutions  of  the  silver  salts 
are  precipitated  black  by  hydrogen  sulphide  and  by  ammonium 
sulphide. 

Potassium  hydrate  forms  an  olive-green  precipitate  of  silver 
oxide,  insoluble  in  excess.  Ammonia  does  not  precipitate  them. 

Hydrochloric  acid  and  the  soluble  chlorides  form  a  white 
precipitate  of  silver  chloride,  insoluble  in  either  cold  or  boiling 
nitric  acid,  but  soluble  in  ammonia. 

Potassium  iodide  gives  a  yellow  precipitate,  almost  insoluble 
in  ammonia. 

Silvering. — This  operation  consists  in  covering  the  common 
metals  or  glass  with  a  coating  of  silver  more  or  less  thick. 

The  metals  are  silvered  by  either  amalgamation  or  galvanic 
deposition.  In  the  latter  and  preferable  operation,  a  solution 
of  the  double  cyanide  of  silver  and  potassium  is  generally  used. 

Mirrors  and  glass  articles  in  general  are  silvered  by  the  re- 
duction of  a  silver  salt  by  aldehyde,  glucose,  or  tartaric  acid. 
The  following  receipt  is  given  by  Liebig:  a  solution  of  10 
grammes  of  silver  "nitrate  is  supersaturated  with  ammonia  and 
rendered  strongly  alkaline  by  caustic  soda.  The  volume  of 
the  liquid  should  be  1450  c.c.  Another  solution  is  prepared 
by  dissolving  1  part  of  milk  sugar  in  10  parts  of  water.  The 
latter  solution  is  mixed  with  its  own  volume  of  the  first  solu- 
tion, and  the  glass  to  be  silvered  is  washed  with  alcohol  and 
immersed  in  the  liquid.  The  reduction  of  the  silver  salt  begins 
immediately,  and  does  not  require  the  aid  of  heat. 

The  experiment  may  easily  be  made  in  a  glass  flask,  the 
interior  of  which  will  be  uniformly  silvered. 

Assaying  of  Silver. — This  name  is  applied  to  the  methods 
which  serve  for  the  analysis  of  alloys  of  silver  and  copper,  such 
as  coin,  medals,  silverware,  and  jewelry.  The  assay  may  be 
conducted  by  the  dry  way  or  by  the  wet  way. 

The  dry  assay  consists  in  the  operation  called  cupellation 
(Fig.  118).  A  certain  quantity  of  metallic  lead  is  melted  in 
a  cupel  of  bone-ash  in  a  reverberatory  furnace,  and  a  weighed 
quantity  of  the  alloy  of  silver  and  copper,  carefully  wrapped 
in  a  small  piece  of  paper,  is  placed  upon  the  fused  metal.  The 
silver  dissolves  in  the  melted  lead,  and  a  ternary  alloy  is  thus 
obtained  which  is  exposed  to  the  action  of  air  at  a  red  heat. 

33* 


390 


ELEMENTS   OP   MODERN    CHEMISTRY. 


Under  these  conditions,  the  lead  and  copper  become  oxidized ; 
the  oxide  of  lead  fuses,  and  the  melted  litharge,  which  should 
be  in  great  excess  in  proportion  to  the  oxide  of  copper,  dis- 
solves the  latter,  and  with  it  is  absorbed  by  the  porous  cupel. 
The  phenomenon  of  brightening  (page  360)  indicates  the  ter- 
mination of  the  process. 


FIG.  118. 

The  wet  assay,  invented  by  Gay-Lussac,  consists  in  adding 
to  a  solution  in  nitric  acid  of  a  known  weight  of  the  alloy  of 
silver  and  copper,  a  titered  solution  of  sodium  chloride,  that 
is,  a  solution  containing  an  exactly  known  weight  of  salt  in  one 
litre  of  water.  This  solution  is  cautiously  added  until  it  no 
longer  precipitates  silver  chloride,  and  the  quantity  of  silver 
present  is  calculated  by  the  volume  of  the  titered  solution  that 
has  been  required  to  completely  precipitate  the  silver  in  the 
form  of  chloride.  As  the  latter  readily  deposits  from  a  liquid 
that  is  carefully  agitated,  it  is  easy  to  catch  the  termination 
of  the  operation,  that  is,  the  precise  moment  when  all  of  the 
silver  is  precipitated  and  the  addition  of  the  titered  liquid 
must  be  arrested. 


GOLD.  391 

Process. — Two  titered  solutions  are  used  to  precipitate  the 
silver:  1st,  a  normal  solution,  containing  0.5417  gramme  of 
sodium  chloride  per  decilitre,  a  quantity  sufficient  to  precipitate 
one  gramme  of  silver ;  2d,  a  decinormal  solution,  that  is,  one 
containing  the  same  quantity  of  sodium  chloride  per  litre,  so 
that  1  c.c.  of  this  liquid  will  precipitate  one  milligramme 
of  silver.  To  analyze  an  alloy  of  silver,  a  coin,  for  example, 
such  a  quantity  is  weighed  as  would  contain  one  gramme  of 
silver,  if  the  proportion  of  silver  were  a  little  less  than  the 
extreme  limit  allowed.  If  the  alloy  ought  to  contain  900 
thousandths  of  pure  silver,  with  a  tolerance  of  2  thousandths, 
it  would  be  rejected  should  it  contain  only  897  thousandths. 

We  suppose,  however,  that  the  latter  is  its  quality,  and 
weigh  a  quantity  of  the  alloy  which  would  then  contain  one 
gramme  of  pure  silver,  that  is,  1.1148  grammes.  This  alloy 
is  dissolved  in  nitric  acid,  and  one  decilitre  of  the  normal  solu- 
tion is  added.  All  of  the  silver  should  not  be  precipitated,  for 
the  standard  of  the  alloy  should  be  above  897.  This  is  deter- 
mined by  adding  to  the  clarified  liquid  one  or  more  cubic  cen- 
timetres of  the  decinormal  solution,  until  the  liquid  ceases  to 
be  troubled  by  a  fresh  addition.  As  each  cubic  centimetre  of 
this  solution  corresponds  to  one  milligramme  of  silver,  we  must 
add  to  the  gramme  of  silver  at  first  precipitated  as  many 
milligrammes  as  we  have  added  cubic  centimetres  of  the  deci- 
normal solution,  the  last  cubic  centimetre  added  counting  for 
only  half  a  milligramme.  Knowing  the  quantity  of  pure  silver 
contained  in  1.1148  grammes  of  the  alloy  analyzed,  the 
standard  of  the  latter  is  determined  by  a  simple  calculation. 


GOLD. 

Au(Aurum)  =  197 

Natural  State. — Gold  is  one  of  the  most  anciently  known 
metals.  It  is  generally  found  in  the  native  state,  either  in 
streaks  or  veins,  or  in  sand.  It  ordinarily  occurs  in  scales  or 
rounded  grains  disseminated  in  alluvial  sands,  or  in  the  rocks 
whose  disintegration  produces  such  sands.  It  is  well  known 
that  gold-dust  is  suspended  in  the  waters  of  certain  rivers. 

Gold  is  sometimes  found  combined  with  silver,  lead,  copper, 
and  tellurium. 


392  ELEMENTS    OF    MODERN    CHEMISTRY. 

Extraction. — Gold  is  extracted  from  auriferous  sand  by 
washings,  which  remove  the  particles  lighter  than  the  gold. 
These  washings  are  conducted  in  wooden  troughs  (cradles),  or 
on  inclined  tables,  the  gold  sinking  to  the  bottom  of  the  cradles 
or  remaining  on  the  tables.  When  it  is  in  particles  too  minute 
to  be  separated  mechanically  from  the  sand,  which  still  remains 
in  small  quantity,  the  whole  is  agitated  with  mercury  ;  the  gold 
dissolves.  The  amalgam  thus  obtained  is  compressed  in  a 
chamois-skin,  which  allows  the  passage  of  the  excess  of  mer- 
cury. When  the  solid  residue  is  distilled  the  gold  remains. 

Auriferous  quartz  rocks  are  crushed  to  powder,  which  is  then 
subjected  to  washings.  Mercury  is  sometimes  employed  to  ex- 
tract the  gold  from  the  pulverized  rock.  The  following  process 
has  been  employed  for  some  years  in  California  and  Australia. 
The  crushed  rock,  with  mercury,  water,  and  two  cast-iron  balls, 
is  introduced  into  basins,  to  which  a  rotating  motion  is  given 
(Fig.  119).  By  the  friction  of  the  balls  it  is  soon  reduced  to 


FIG.  119. 

an  impalpable  powder,  which  remains  suspended  in  the  water, 
and  is  carried  out  with  the  latter  through  openings  in  the  upper 
part  of  the  basins,  while  the  gold  amalgamates  with  the  mer- 
cury. 

Native  gold,  as  well  as  that  extracted  from  different  minerals, 
is  nearly  always  alloyed  with  silver.  The  two  metals  are  sep- 
arated by  the  wet  way,  by  attacking  the  alloy  with  either  nitric 
or  sulphuric  acid.  Nitrate  or  sulphate  of  silver  is  formed,  the 
latter  being  soluble  in  hot  water.  The  gold  remains  in  a  pul- 
verulent state.  It  is  to  be  remarked  that  the  alloy  of  gold  and 
silver  must  be  rich  in  silver  in  order  that  this  process,  called 
refining,  can  be  applied.  Hence  it  is  sometimes  necessary  to 


OXIDES  OF  GOLD — CHLORIDES  OF  GOLD.      393 

increase  the  proportion  of  silver  by  melting  the  alloy  with  that 
metal. 

An  alloy  of  gold  and  silver  rich  in  gold  may  also  be  treated 
with  aqua  regia.  Both  metals  are  converted  into  chlorides; 
that  of  silver  is  insoluble,  while  that  of  gold  dissolves.  When 
ferrous  sulphate  is  added  to  the  yellow  solution  of  chloride  of 
gold,  a  precipitate  of  metallic  gold  is  obtained,  the  chlorine 
acting  upon  the  iron  of  the  ferrous  sulphate  which  is  thus 
transformed  into  ferric  salt. 

Properties  of  Gold. — Pure  gold  has  a  beautiful  yellow  color. 
In  thin  leaves  it  is  translucent,  allowing  the  passage  of  a  green- 
ish light.  Its  density  is  19.5.  It  is  quite  soft,  and  is  the  most 
malleable  and  most  ductile  of  the  metals. 

It  melts  at  1200°,  and  volatilizes  at  a  higher  temperature. 
Its  vapor  is  green. 

It  is  unaltered  by  the  air  at  all  temperatures.  Sulphuric, 
hydrochloric,  nitric,  and  phosphoric  acids  have  no  action  on  it 
either  in  the  cold  or  when  aided  by  heat.  It  is  dissolved  by 
nitro-hydrochloric  acid. 

Some  gold  leaf  may  be  boiled  with  hydrochloric  acid  in  a 
test-tube ;  the  gold  will  resist  the  action  of  the  acid,  and  will 
retain  its  lustre.  Some  more  gold  leaf  may  be  boiled  with  pure 
nitric  acid  in  another  tube,  and  again  the  metal  will  not  be 
attacked.  But  on  mixing  the  two  liquids,  the  gold  will  be  dis- 
solved with  disengagement  of  red  vapors.  Gold  trichloride  will 
be  formed,  and  will  color  the  liquid  yellow. 

OXIDES  OF   GOLD. 

There  are  two  compounds  of  gold  and  oxygen,  a  monoxide, 
Au20,  and  a  trioxide,  Au203.  The  latter  forms  compounds 
with  the  bases.  When  magnesia  is  added  to  solution  of  auric 
chloride,  an  insoluble  yellow  precipitate  of  magnesium  aurate 
is  formed ;  when  this  is  decomposed  by  nitric  acid  it  leaves  auric 
hydrate.  This  hydrate  is  yellow ;  it  easily  parts  with  its  water, 
and  is  converted  into  a  brown-black  powder  of  auric  oxide. 
The  latter  is  not  stable,  being  decomposed  by  light  and  by  a 
temperature  of  about  250°. 

CHLORIDES  OF   GOLD. 

Aurous  chloride,  AuCl,  is  obtained  as  an  insoluble  yellow 
powder  by  heating  auric  chloride  to  230°. 
B* 


394  ELEMENTS   OF   MODERN   CHEMISTRY. 

Auric  chloride  or  trichloride  of  gold,  AuCP,  is  prepared  by 
dissolving  the  metal  in  aqua  regia.  After  concentration  the 
liquid  solidifies,  on  cooling,  to  a  dark-red,  crystalline  and  deli- 
quescent mass. 

The  solution  of  auric  chloride  is  yellowish-brown  when  con- 
centrated, pure  yellow  when  dilute.  It  is  decomposed  by  light. 
It  colors  the  skin  violet,  and  is  reduced  by  a  great  number  of 
bodies.  Phosphorus,  and  hypophosphorous,  phosphorous  and 
sulphurous  acids  precipitate  from  it  metallic  gold.  It  is  the 
same  with  most  of  the  metals,  which  combine  with  the  chlorine, 
setting  free  the  gold.  A  brown  precipitate  of  metallic  gold  is 
immediately  obtained  on  adding  a  solution  of  ferrous  sulphate 
to  a  solution  of  auric  chloride.  Auric  chloride  dissolves  in 
ether,  which  removes  it  from  its  aqueous  solution  when  the 
two  liquids  are  agitated  together. 

If  a  solution  of  auric  chloride  be  added  to  a  mixture  of 
stannous  and  stannic  chlorides  in  solution,  a  flocculent  precipi- 
tate of  a  purple  color,  more  or  less  pure  according  to  the  con- 
centration of  the  solutions  and  the  proportions  of  the  mixture, 
will  be  formed.  It  is  purple  of  Cassius,  a  compound  employed 
in  painting  on  glass  and  porcelain.  It  contains  tin,  gold,  oxy- 
gen, and  hydrogen,  but  its  constitution  is  not  well  known. 

Auric  chloride  forms  crystalline  compounds  with  the  alkaline 
chlorides.  When  a  mixture  of  chloride  of  gold  and  sodium 
chloride  is  evaporated  until  a  pellicle  forms  on  its  surface,  yellow 
crystals  containing  NaCl.  AuCP  -J-  2H2O,  are  formed  on  cooling. 

Gilding. — Several  processes  are  used  for  gilding  metals,  such 
as  silver  and  copper.  The  objects  may  be  gilded  by  amalga- 
mation, by  dipping,  or  by  galvanic  deposition. 

Gilding  by  Amalgamation. — Grold  readily  alloys  with  mer- 
cury, and  the  amalgam  is  used  for  gilding  objects  of  silver  and 
copper.  The  pieces  are  heated  to  destroy  greasy  matters,  and 
are  then  cleaned  by  dipping  them  into  dilute  sulphuric  acid, 
after  which  they  are  washed  and  dried  with  saw-dust.  They 
are  then  rubbed  with  a  brush  of  brass  wires  dipped  into  a  solu- 
tion of  mercurous  nitrate,  and  then  with  a  brush  impregnated 
with  an  amalgam  of  one  part  of  gold  and  eight  parts  of  mer- 
cury. They  are  afterwards  heated  to  volatilize  the  mercury, 
an  operation  dangerous  to  the  health  of  the  workmen,  and  which 
should  be  conducted  in  a  furnace  having  a  good  draught.  The 
pieces  thus  gilded  are  dull ;  they  become  lustrous  after  suitable 
washings  and  polishings. 


PLATINUM.  395 

Gilding  by  Dipping. — Copper  objects  may  be  covered  with 
a  thin  film  of  gold  by  dipping  them  into  a  boiling  solution  of 
carbonate  and  phosphate  of  sodium  to  which  auric  chloride 
has  been  added. 

Electro- Gilding. — The  copper  objects,  previously  heated  and 
cleaned  by  dilute  sulphuric  acid,  are  plunged  for  a  few  seconds 
into  dilute  nitric  acid  and  then  wiped  dry.  They  are  then 
connected  with  the  negative  pole  of  a  battery  and  dipped  into 
a  bath  composed  of  1  (part  of  cyanide  of  gold,  10  parts  of  potas- 
sium cyanide,  and  100  parts  of  water.  A  plate  of  gold  plunged 
into  the  same  bath  constitutes  the  positive  pole.  When  the 
current  passes,  the  objects  become  covered  with  a  uniform  and 
adherent  coating  of  gold.  As  the  metal  is  precipitated  from 
the  solution,  it  is  replaced  by  an  equivalent  quantity  from  that 
which  constitutes  the  positive  pole,  and  which  dissolves.  The 
bath  thus  retains  a  constant  composition.  The  same  process 
is  applicable  to  electro-silvering. 

Assaying  of  Gold  Alloys. — Gold  is  assayed  by  cupellation. 
The  alloy  is  first  melted  with  silver,  so  that  the  quantity  of  the 
latter  metal  present  may  be  at  least  triple  that  of  the  gold. 
This  alloy  is  submitted  to  cupellation,  an  operation  which 
presents  no  difficulty,  for  gold  rich  in  silver  does  not  spit. 
The  button  is  hammered  out  to  a  thin  sheet,  reheated  and 
formed  into  a  little  cornet,  which  is  introduced  into  a  small 
flask  and  heated  with  nitric  acid  of  22°  Baume.  After  several 
minutes'  boiling  the  greater  part  of  the  silver  is  dissolved ;  the 
liquid  is  then  decanted  and  replaced  by  more  concentrated  nitric 
acid.  All  of  the  silver  dissolves  and  the  gold  remains  in  the 
form  of  a  but  slightly  coherent  cornet.  It  is  washed,  heated  to 
redness  in  a  crucible  to  give  it  coherence,  and  finally  weighed. 


PLATINUM. 

Pt  =  107.5 

Natural  State  and  Treatment  of  Platinum  Ores. — Plat- 
inum is  found  native,  generally  in  alluvial  sands.  Its  principal 
deposits  are  in  the  Ural  Mountains,  Brazil,  and  New  Granada. 
The  platinum  ore,  extracted  from  the  sand  by  washing,  contains, 
independently  of  73  to  86  per  cent,  of  platinum,  various  other 
metals,  such  as  iridium,  palladium,  rhodium,  osmium,  ruthenium, 
gold,  iron,  and  copper;  an  alloy  of  osmium  and  iridium,  and 


396  ELEMENTS   OF   MODERN   CHEMISTRY. 

various  minerals,  such  as  titaniferous  iron,  chrome  iron,  pyrites, 
etc.  The  ore  is  well  washed  to  remove  the  sand,  and  treated 
with  dilute  aqua  regia  which  dissolves  the  gold,  iron,  and  cop- 
per; it  is  then  heated  with  concentrated  hydrochloric  acid  and 
nitric  acid  is  gradually  added.  The  aqua  regia  dissolves  the 
platinum  and  certain  of  its  accompanying  metals,  leaving  the 
osmium  and  iridium.  The  solution  is  neutralized  with  sodium 
carbonate  and  treated  with  a  solution  of  cyanide  of  mercury, 
which  precipitates  palladium  cyanide.  A  solution  of  ammo- 
nium chloride  is  added  to  the  filtered  liquid,  and  forms  an 
abundant  precipitate  of  ammonium  and  platinum  double  chlo- 
ride, which  is  generally  mixed  with  a  small  quantity  of  ammo- 
nium and  iridium  double  chloride.  This  precipitate  is  calcined 
at  a  dull-red  heat,  and  leaves  a  dull-gray,  spongy  residue.  It 
is  spongy  platinum.  It  contains  a  small  quantity  of  iridium. 

To  give  coherence  to  this  sponge  and  convert  it  into  a  mal- 
leable and  ductile  metal,  it  is  reduced  to  powder  in  a  wooden 
mortar  and  triturated  with  enough  water  to  convert  it  into  a 
perfectly  homogeneous  paste.  This  paste  is  introduced  into  a 
slightly-conical  cylinder  of  brass  or  iron,  and  compressed  first 
with  a  wooden  piston,  then  by  a  steel  rod.  The  compression 
is  finished  by  the  aid  of  a  hydraulic  press,  and  the  slightly- 
conical  cylinders  so  formed  are  heated  to  whiteness  and  forged 
under  the  hammer,  as  iron  is  forged. 

H.  Sainte-Claire  Deville  and  Debray  have  recently  extracted 
the  metal  by  simple  fusion  of  the  ore.  The  fusion  is  effected 
in  a  lenticular  cavity  cut  in  two  large  masses  of  quick-lime, 
placed  one  above  the  other.  A  current  of  illuminating  gas  is 
directed  into  this  furnace,  and  the  combustion  is  supported  by 
a  continual  supply  of  oxygen. 

Properties  of  Platinum. — Platinum  has  a  grayish-white 
lustre.  It  melts  only  at  the  highest  attainable  temperatures. 
The  density  of  the  cast  metal  is  21.1 ;  that  of  the  forged  metal 
21.5.  It  softens  at  a  white  heat,  and  can  then  be  forged  and 
welded  like  iron. 

The  experiments  of  H.  Deville  and  Troost  have  shown  that  a 
red-hot  platinum  tube  allows  hydrogen  to  pass  through  its  pores. 

Platinum  has  the  curious  property  of  condensing  gases  on  its 
surface,  and  this  property  is  the  cause  of  certain  chemical  phe- 
nomena that  were  formerly  attributed  to  mere  contact  of  the 
metal. 

If  a  morsel  of  platinum-sponge  be  introduced  into  a  small 


CHLORIDES    OF   PLATINUM.  397 

jar  filled  with  an  explosive  mixture  of  oxygen  and  hydrogen, 
the  gases  will  combine  instantly,  with  explosion. 

This  property  is  most  highly  developed  in  platinum-black, 
for  in  this  form  the  metal  exists  in  an  extreme  state  of 
division.  It  may  be  prepared  by  reducing  a  solution  of 
platinic  chloride  by  zinc ;  or  platinum  dichloride  may  be  boiled 
with  potassium  hydrate,  and  alcohol  or  a  solution  of  sugar 
gradually  added  to  the  liquid,  which  must  be  continually 
stirred.  The  platinum  is  precipitated  as  a  black  powder. 

Platinum  is  unaltered  by  the  air.  It  is  not  attacked  by 
either  nitric,  hydrochloric,  or  sulphuric  acids,  even  boiling.  ^  It 
dissolves  in  aqua  regia.  The  alkaline  hydrates  attack  it  at  high 
temperatures  on  contact  with  the  air.  It  is  the  same  with  the 
alkaline  nitrates. 

There  are  two  oxides  of  platinum,  a  monoxide,  PtO,  and  a 
dioxide,  PtO2. 

CHLORIDES   OF  PLATINUM. 

These  are  the  more  important  compounds  of  platinum. 
There  are  two,  a  dichloride,  PtCl2,  and  a  tetrachloride,  PtCl*. 

Platinum  dichloride  is  obtained  by  cautiously  heating  the 
tetrachloride  to  200  D.  Chlorine  is  disengaged,  and  after  cool- 
ing, the  residue  is  exhausted  with  boiling  water,  which  leaves 
an  olive-green  powder,  constituting  the  dichloride.  When 
ammonia  is  added  to  a  solution  of  platinum  dichloride  in 
hydrochloric  acid,  a  green,  crystalline  powder  separates  after 
some  time.  It  is  called  green  salt  of  Magnus,  and  contains 

PtCl2  -f  2NH3 

It  maybe  regarded  as  the  dichloride  of  platinoso-diammonium. 
Pt" 

H2 
H2 

It  is  derived  from  two  molecules  of  ammonium  chloride  by 
the  substitution  of  an  atom  of  diatomic  platinum  for  two  atoms 
of  hydrogen. 

Platinum  tetrachloride,  or  platinic  chloride,  PtCl4,  is 
formed  when  platinum  is  dissolved  in  aqua  regia.  A  red- 
brown  solution  is  obtained,  which,  after  concentration  and  cool- 
ing, deposits  red-brown  needles  of  hydrated  platinic  chloride. 

34 


398  ELEMENTS   OP   MODERN   CHEMISTRY. 

The  crystals  lose  their  water  when  heated,  and  are  converted 
into  a  dark,  red-brown  mass,  which  constitutes  the  anhydrous 
chloride  PtCl*.  This  body  absorbs  moisture  when  exposed  to 
the  air.  It  is  very  soluble  in  water,  alcohol,  and  ether. 

If  a  solution  of  ammonium  chloride  be  added  to  a  solution 
of  platinic  chloride,  a  yellow,  crystalline  precipitate  of  plati- 
num and  ammonium  double  chloride  is  immediately  formed. 
This  body  is  but  little  soluble  in  cold  water,  but  more  soluble 
in  boiling  water,  from  which  it  is  deposited  in  microscopic, 
regular  octahedra.  It  is  almost  insoluble  in  alcohol.  It  contains 

PtCl4.2NH4Cl 

A  yellow,  crystalline  precipitate  of  double  chloride  of  plati- 
num and  potassium  is  obtained,  in  the  same  manner,  on  adding 
a  solution  of  platinic  chloride  to  a  solution  of  a  potassium  salt, 
if  the  liquids  be  not  too  dilute. 

PtCl4.2KCl 


ORGANIC  CHEMISTRY. 


GENERAL  IDEAS  UPON  THE   CONSTITUTION 
OF  ORGANIC   COMPOUNDS. 

ORGANIC  CHEMISTRY  studies  the  history  of  the  compounds 
of  carbon.  The  most  simple  of  these  are  the  gases  carbon 
monoxide  and  carbon  dioxide  ;  each  contains  but  a  single  atom 
of  carbon.  In  this  respect  they  resemble  the  inflammable  gas 
which  is  disengaged  from  the  mud  of  marshes  ;  it  contains  one 
atom  of  carbon  combined  with  four  atoms  of  hydrogen. 

The  gas  hydrogen  dicarbide  or  ethylene,  which  has  already 
been  mentioned,  contains  two  atoms  of  carbon  united  with  four 
atoms  of  hydrogen.  A  great  number  of  compounds  are  known 
which  contain  only  carbon  and  hydrogen,  and  they  are  called 
hydrocarbons  or  carburetted  hydrogens.  The  atoms  of  carbon 
are  aggregated  in  them,  together  with  the  atoms  of  hydrogen. 
Other  elements  are  often  added  to  the  preceding,  forming 
molecules  more  or  less  complex.  The  carbon  atoms  form  as  it 
were  the  framework,  and  the  carbon  compounds  possess  pecu- 
liar properties  precisely  on  account  of  the  easy  facility  with 
which  the  atoms  of  carbon  accumulate  in  one  and  the  same 
molecule,  and  link  themselves  in  some  manner  one  to  another. 
The  following  developments  will  give  some  idea  of  the  mode 
of  generation  and  the  structure  of  organic  molecules. 

The  most  Simple  Organic  Compounds. — Their  Composi- 
tion proves  Carbon  to  be  a  Tetratomic  Element. — The  most 
simple  of  the  hydrocarbons  is  marsh  gas. 

When  this  gas  is  submitted  to  the  action  of  chlorine,  one  or 
more  atoms  of  hydrogen  may  be  removed  from  it ;  they  com- 
bine with  the  chlorine  and  are  disengaged  in  the  form  of  hy- 
drochloric acid  gas.  The  curious  fact,  first  noticed  by  Dumas, 
is  then  observed,  that  each  atom  of  hydrogen  which  is  removed 
is  replaced  by  an  atom  of  chlorine.  This  substitution  gives 


400  ELEMENTS   OF   MODERN   CHEMISTRY. 

rise  to  a  series  of  chlorinated  compounds,  which  present  the 
most  simple  relations  with  marsh  gas.  The  latter  contains  only 
carbon  and  hydrogen.  The  chlorine  compounds  derived  from 
it  by  substitution,  form  with  it  the  following  series : 

CH*       marsh  gas,  or  methane. 

CH3CI    monochloromethane  (methyl  chloride). 

CH2C12  dichloromethane  (methylene  chloride). 

CHC13   trichloromethane  (chloroform). 

CC14      tetrachloromethane  (carbon  tetrachloride). 

In  each  of  these  compounds  a  single  atom  of  carbon  is  united 
with  four  monatomic  atoms.  We  have  seen  that  the  atoms  of 
chlorine  and  hydrogen  are  equivalent  as  regards  their  power 
of  combination.  In  the  preceding  compounds,  the  sum  of  the 
atoms  of  hydrogen  and  chlorine  which  are  combined  with  one 
atom  of  carbon  is  invariably  four,  and  this  number  cannot  be 
exceeded.  But  two  atoms  of  a  monatomic  element  may  be  re- 
placed by  one  atom  of  a  diatomic  element.  One  atom  of  car- 
bon, which  unites  with  four  atoms  of  hydrogen  or  chlorine, 
may  unite  with  two  atoms  of  oxygen  to  form  carbon  dioxide 

CO"2 

and  this  compound  is  saturated  like  those  preceding,  for  ono 
atom  of  oxygen  is  equivalent  to  two  atoms  of  hydrogen  or 
chlorine.  In  carbon  monoxide,  CO",  the  affinity  of  carbon  is 
not  satisfied ;  hence  this  gas  will  unite  directly  with  an  atom 
of  oxygen  to  form  carbon  dioxide,  or  with  two  atoms  of  chlo- 
rine to  form  chloro-carbqnic  gas. 

CO"CP 

In  ammonia,  one  atom  of  nitrogen  is  combined  with  three 
atoms  of  hydrogen ;  nitrogen  is  triatomic ;  hence  it  may  replace 
three  atoms  of  hydrogen.  A  body  is  known  which  represents 
marsh  gas,  in  which  three  atoms  of  hydrogen  are  replaced  by 
one  atom  of  nitrogen.  This  is  the  dangerous  poison  known  as 
prussic  or  hydrocyanic  acid,  and  the  composition  of  which  is 
represented  by  the  formula 

CN'"H 

In  all  of  the  compounds  which  have  just  been  mentioned  a 
single  atom  of  carbon  is  invariably  united  to  a  number  of  ele- 
ments of  which  the  united  atomicities  is  always  four,  and  never 
more  nor  less  than  that  number.  It  is  then  reasonable  to 
conclude  that  in  them  carbon  plays  the  part  of  a  tetratomic 


INTRODUCTION   TO   ORGANIC   CHEMISTRY.  401 

element.  This  important  fact,  first  exposed  by  Kekule,  can  be 
clearly  understood  if  we  represent  the  preceding  atomic  formulae 
in  a  graphic  manner,  that  is,  by  symbols  so  arranged  as  to  show 
the  reciprocal  relations  of  the  atoms  and  their  mutual  satura- 
tion. In  these  formulae  a  saturated  atomicity  is  indicated  by 
a  line  of  union,  two  atomicities  by  two  lines,  etc. 

H  H  H  Cl 

H-C-H  H-C-C1          C1-C-C1          C1-6-C1 


4 


A 


Marsh  gas.  Monochloro-        Trichloromethane.  Carbon 

methane.  (Chloroform.)  tetrachloride. 

Cl 

o=c=o          ci-dtp          H-C_-N 

Carbon  dioxide.          Chlorocarbonic  gas.          Hydrocyanic  acid. 

There  exists  a  very  volatile,  ethereal  liquid,  which  represents 
marsh  gas,  in  which  one  atom  of  hydrogen  is  replaced  by  iodine. 
It  is  the  body  known  as  methyl  iodide,  CH3I. 

If  this  body  be  heated  for  a  long  time  in  a  sealed  tube  with 
a  solution  of  potassium  hydrate,  potassium  iodide  will  be  grad- 
ually formed,  and  the  solution  will  contain  a  volatile,  spirituous 
liquid  which  can  easily  be  separated  by  distillation,  for  it  boils 
at  66°.  It  is  the  same  body  which  constitutes  the  most  vola- 
tile of  the  liquids  which  are  formed  in  the  destructive  distilla- 
tion of  wood  ;  it  is  called  wood  spirit,  and  its  chemical  name  is 
methylic  alcohol. 

The  reaction  by  which  it  is  formed  is  very  simple.  The 
iodine  of  the  methyl  iodide  combines  with  the  potassium  ;  but 
when  this  iodine  is  removed,  the  carbon  remains  united  to  but 
three  atoms  of  hydrogen.  It  is  no  longer  saturated,  and  it 
therefore  combines  with  the  oxygen  and  hydrogen  which  were 
united  with  the  potassium  in  the  potassium  hydrate. 

CH3I  +  KOH  =  CH8.OH  +  KI 

It  will  be  seen  that  the  atom  of  oxygen  alone  does  not  com- 
bine with  the  group  CH3,  which  is  called  methyl.  It  is  accom- 
panied by  an  atom  of  hydrogen,  with  which  it  remains  united 
in  the  new  compound  which  is  called  methyl  hydrate  or 
methylic  alcohol.  As  has  been  said,  this  oxygen  replaces  the 
iodine  in  the  iodide  of  methyl,  but  as  it  possesses  two  atomici- 
ties, and  the  carbon  already  united  with  H3  has  only  one  free 
atomicity,  the  atom  of  oxygen  can  only  fix  upon  the  carbon  by 

34* 


402  ELEMENTS   OP   MODERN    CHEMISTRY. 

one  of  its  atomicities ;  the  other  remains  saturated  by  the  atom  of 
hydrogen.  The  latter  is  then  drawn  into  the  combination,  and  is 
united,  not  to  the  carbon,  but  to  the  oxygen.  The  reaction  takes 
place  as  if  the  atom  of  iodine  were  replaced  by  the  group  hy- 
droxyl  (OH)  which  is  monatomic.  Hence  the  relations  between 
the  atoms  in  methyl  hydrate  are  represented  by  the  formula 

H 

H-t-(OH)' 

H 

If  we  compare  the  constitution  of  the  three  bodies  CH3C1, 
CH3I,  CH3(OH),  we  notice  that  they  contain  a  common  ele- 
ment, namely,  the  group  CH3,  which  is  united  to  chlorine,  to 
iodine,  or  to  hydroxyl.  Besides  this,  experiment  has  shown 
us  that  methyl  iodide  can  be  transformed  into  hydrate.  The 
group  methyl  hence  presents  a  certain  stability  and  can  pass 
from  one  combination  to  another.  This  is  expressed  by  saying 
that  it  is  a  radical. 

If  methyl  iodide  be  heated  with  an  aqueous  solution  of 
ammonia,  among  the  products  formed  will  be  found  the  hydri- 
odide  of  a  base  which  represents  ammonia  in  which  one  atom 
of  hydrogen  is  replaced  by  the  group  methyl.  Potassium 
hydrate  sets  this  base  at  liberty.  At  ordinary  temperatures 
and  pressures,  it  constitutes  a  gas,  very  soluble  in  water  and 
possessing  a  strong  ammoniacal  odor.  It  is  methylamine.  The 
reaction  by  which  it  is  formed  is  as  follows :  the  iodine  with- 
draws one  atom  of  hydrogen  from  the  ammonia,  which  atom 
of  hydrogen  is  replaced  by  the  group  CH3. 

CH3I  +  NH3  ==  CH3(NH2).HI. 

Methylamine  hydriodide. 

In  methylamine  then,  the  fourth  atomicity  of  the  carbon 
atom  is  saturated  by  nitrogen,  but  as  this  element  is  triatomic 
it  brings  into  the  combination  two  atoms  of  hydrogen  which 
saturate  its  two  other  atomicities.  It  may  then  be  said  that 
in  methylamine  the  fourth  atomicity  of  carbon  is  saturated  by 
the  group  NH2.  This  is  expressed  in  the  following  formulae. 

H  II 

H-C-N=H2    =    H-C-(NH2)' 
H  H 

Methylamine. 


INTRODUCTION   TO   ORGANIC   CHEMISTRY.  403 

Generation  of  Hydrocarbons  containing  Several  Atoms 
of  Carbon.  —  The  preceding  compounds  contain  but  a  single 
atom  of  carbon,  but  starting  with  one  of  these  compounds  we 
may  produce  more  complicated  organic  molecules  containing 
several  carbon  atoms. 

If  methyl  iodide  be  heated  with  sodium  in  sealed  tubes, 
sodium  iodide  is  formed,  and  a  gas,  a  hydrocarbon,  is  confined 
under  great  pressure  in  the  tubes.  This  gas  escapes,  and  may 
be  collected,  when  the  drawn-out  points  of  the  tubes  are  opened 
in  the  blow-pipe  flame.  It  is  dimethyl,  and  has  been  formed 
according  to  the  following  reaction  : 


2CH3I     -f     Na2     =     C2H6     +     2NaI 

Methyl  iodide.  Dimethyl,  or  ethane. 

Two  molecules  of  methyl  iodide  have  entered  into  the  reac- 
tion, and  the  whole  of  the  carbon  of  these  two  molecules  is 
found  in  one  molecule  of  the  hydrocarbon,  C2H6  =  (CH3)2, 
which  results. 

On  losing  their  iodine  the  two  methyl  groups  combine  to- 
gether. One  of  the  carbon  atoms  attracts  the  other,  exchanging 
with  it  the  fourth  atomicity  set  free  by  the  loss  of  the  iodine. 
Hence  the  iodine  of  one  of  the  molecules  of  methyl  iodide  has 
been  replaced  by  the  carbon  of  the  other,  which  fixes  upon  the 
group  CH3  by  a  single  one  of  its  atomicities,  and  at  the  same 
time  brings  into  the  combination  the  three  atoms  of  hydrogen 
which  saturate  the  other  three  atomicities.  This  is  expressed 
in  the  following  formulae  : 

H  H  H  H 

H-C-H  H-C-I  H-C-C-H 

i  i  ii 

H  H  HH 

Methane  (methyl  hydride).        Methyl  iodide.    Dimethyl  (ethyl  hj'dride  or  ethane). 

The  mode  of  generation  of  this  new  hydrocarbon,  which 
contains  two  atoms  of  carbon,  is  worthy  of  consideration.  It 
results  from  the  substitution  of  a  methyl  group  for  one  atom  of 
hydrogen  in  methyl  hydride.  One  atom  of  carbon,  accompa- 
nied by  three  atoms  of  hydrogen,  fixes  upon  another  atom  of 
carbon  of  which  it  completes  the  saturation.  By  this  exchange 
of  atomicities  each  of  the  carbon  atoms  retains  only  three  affin- 
ities which  are  satisfied  by  three  atoms  of  hydrogen.  The 
two  methyl  groups,  CH3  -f-  CH3  =  C2H6,  are  then  united  by 
their  carbon  atoms,  and  are  held  together  by  the  affinity  of 


404  ELEMENTS   OP   MODERN   CHEMISTRY. 

carbon  for  carbon.  In  methyl  hydrate  the  group  hydroxyl  is 
bound  to  the  group  CH3  by  the  affinity  of  carbon  for  oxygen. 
In  methylamine,  the  group  NH2  is  united  to  the  group  CH3  by 
the  affinity  of  carbon  for  nitrogen.  In  dimethyl,  it  is  carbon 
which  is  united  to  carbon.  This  has  before  been  expressed  by 
saying  that  the  atoms  of  this  element  possess  a  faculty  to  accu- 
mulate in  one  and  the  same  molecule. 

It  is  in  this  curious  property  that  must  be  sought  the  reason 
for  the  existence  of  those  innumerable  compounds,  more  or  less 
rich  in  atoms  of  carbon,  which  constitute  the  immense  field  of 
organic  chemistry. 

But  it  is  important  to  study  by  new  examples  this  mode  of 
formation  of  organic  compounds. 

Dimethyl,  which  we  have  seen  is  produced  by  the  action  of 
sodium  upon  methyl  iodide,  is  also  known  as  ethyl  hydride.  If 
one  of  its  atoms  of  hydrogen  be  replaced  by  an  atom  of  chlo- 
rine, ethyl  chloride,  C2H5C1,  is  obtained.  Ethyl  iodide,  C2H5I, 
represents  ethyl  hydride,  in  which  one  atom  of  hydrogen  has 
been  replaced  by  iodine. 

If  a  mixture  of  methyl  iodide  and  ethyl  iodide  be  heated 
with  sodium,  among  the  products  of  the  reaction  will  be  found 
a  gas  containing  C3H8 ;  it  is  the  methylide  of  ethyl,  resulting 
from  the  combination  of  methyl,  CH3,  with  the  group  ethyl, 
C2H5.  It  represents  ethyl  iodide  in  which  the  atom  of  iodine 
has  been  replaced  by  a  methyl  group,  the  carbon  of  the  latter 
group  being  fixed  by  one  of  its  atomicities  to  one  of  the  carbon 
atoms  of  the  group  C2H5. 

In  the  same  manner,  by  heating  a  mixture  of  propyl  iodide, 
C3H7I,  and  methyl  iodide  with  sodium,  we  may  add  to  the 
propyl  group,  C3H7,  a  new  atom  of  carbon  escorted  by  its  three 
atoms  of  hydrogen. 

HH  HHH  HHHH 

ii  ill  i     i    i     i 

H-C-C-I  H-C-C-C-H  H-C-C-C-C-H,  etc. 

ii  ill  i    i    i    i 

HH  HHH  HHHH 

Ethyl  iodide.        Methyl-ethyl  (propane).    Methyl-propyl  (butane). 

Nothing  prevents  the  continuation  of  these  additions  of  car- 
bon to  incomplete  hydrocarbons,  that  is,  to  the  residues  of  the 
subtraction  of  iodine  from  the  saturated  iodides,  of  which  the 
following  are  the  names  and  formulae : 

CH3I  C2H5I  C3H7I  C4H9I      C5HUI,  etc. 

Methyl  iodide.        Ethyl  iodide.        Propyl  iodide.        Butyl  iodide.      Amyl  iodide. 


INTRODUCTION   TO   ORGANIC   CHEMISTRY.  405 

The  following  hydrocarbons  would  then  be  formed  succes- 
sively : 


C2H5-CH»    C8H*-CH3    C*H9-CH»    C5Hll-CH3,  etc, 

Methyl-methyl    Methyl-ethyl    Methyl-propyl    Methyl-hutyl      Methyl-amyl 
(Ethane).  (Propane).  (Butane).  (Pentane).  (Hexane). 

In  all  of  these  cases,  the  atoms  of  carbon  united  together 
form,  as  it  were,  a  continued  chain,  and  the  atoms  of  hydrogen 
are  grouped  around  them  as  satellites. 

Homologous  Bodies.  —  Very  simple  relations  exist  between 
the  hydrocarbons  of  which  we  have  just  studied  the  mode  of 
formation.  They  form  a  series  of  which  each  member  differs 
from  the  preceding  by  the  addition  of  CH2.  These  relations 
will  appear  clearly  if  the  formulae  already  given  be  replaced 
by  the  crude  formulae  : 

CH4    methane. 
C2H6    ethane. 
C3H8    propane. 
C4H10  butane. 
C5H12  pentane. 

This  group  of  hydrocarbons  constitutes  what  is  called  the 
homologous  series  of  marsh  gas,  or  the  series  C"H2n+2. 

Many  other  series  are  known,  the  terms  of  which  are  related 
to  each  other  in  the  same  manner,  and  the  bodies  which  form 
part  of  them  may  present  the  greatest  differences  in  composition. 
Sometimes  they  contain  only  carbon  and  hydrogen.  Again, 
they  may  contain  oxygen  or  nitrogen  in  addition  to  these  ele- 
ments ;  in  this  case  the  former  elements  are  united  to  carbon  by 
one  or  more  of  their  atomicities,  as  has  already  been  indicated. 

In  any  organic  body  whatever,  if  an  atom  of  hydrogen  united 
with  carbon  be  replaced  by  a  methyl  group,  CH3,  the  superior 
homologue  of  that  body  is  obtained,  that  is,  the  compound  which 
differs  from  the  original  body  by  the  addition  of  CH2.  There 
is  a  great  resemblance  in  physical  and  chemical  properties 
between  such  homologues. 

Some  of  these  homologous  series  will  be  indicated  farther  on. 

Immediate  Principles  and  Chemical  Species.  —  The  four 
elements,  carbon,  hydrogen,  oxygen,  and  nitrogen,  are  the  more 
ordinary  elements  of  organic  compounds.  Those  which  are 
found  in  nature  in  the  organs  of  plants  and  animals,  and  which 
have  been  called  by  Chevreul  immediate  principles,  contain 
no  others,  excepting  sulphur,  which  exists  in  certain  of  them. 


406  ELEMENTS   OF   MODERN    CHEMISTRY. 

But  nearly  all  of  the  other  elements  can  be  introduced  artificially 
into  organic  compounds ;  it  is  thus  with  bromine,  iodine,  phos- 
phorus, arsenic,  boron,  silicon,  and  a  great  number  of  the  metals. 

In  uniting  with  carbon,  in  different  manners  and  in  various 
proportions,  these  elements  form  an  innumerable  multitude  of 
compounds,  each  of  which  has  a  fixed  composition  and  definite 
properties.  These  bodies  constitute  the  chemical  species,  so  to 
say.  When  submitted  to  the  action  of  reagents,  all  may  be 
modified  in  a  thousand  manners,  and  transformed  into  each 
other.  Sometimes  their  composition  is  simplified,  one  or  more 
carbon  atoms  being  removed  from  the  chain.  Sometimes  it  is 
complicated  by  the  addition  of  new  atoms  of  carbon. 

All  of  these  bodies  contain  carbon,  and  are  distinguished 
from  each  other : 

1.  By  the  number  of  carbon  atoms  contained  in  the  molecule. 

2.  By  the  nature  and  arrangement  of  the  other  atoms  com- 
bined with  the  carbon. 

3.  By  the  arrangement  of  all  of  the  atoms  in  the  molecule. 

The  facts  relative  to  the  atomic  composition  of  organic  com- 
pounds are  obtained  by  elementary  analysis  and  by  the  deter- 
mination of  the  molecular  weight. 

ELEMENTARY   ANALYSIS. 

The  object  of  elementary  analysis  is  the  determination  of 
the  nature  and  proportion  of  the  elements  contained  in  any 
given  organic  body.  We  can  give  here  but  a  summary  descrip- 
tion of  the  processes  employed,  considering  only  those  which 
have  for  object  the  determination  of  carbon,  hydrogen,  and  ni- 
trogen. These,  together,  with  oxygen,  are  the  more  ordinary 
elements  of  organic  combinations. 

In  a  substance  containing  carbon,  hydrogen,  and  oxygen, 
the  first  two  elements  are  determined  directly  in  the  same 
operation ;  the  oxygen  is  determined  by  difference.  When, 
in  addition  to  the  former  elements,  the  body  contains  nitrogen, 
the  determination  of  this  requires  a  separate  operation. 

Determination  of  Carbon  and  Hydrogen.— To  determine 
the  proportion  of  carbon  and  hydrogen  contained  in  100  parts 
of  any  given  organic  substance,  the  carbon  is  converted  into  car- 
bon dioxide,  which  is  collected  and  weighed,  and  the  hydrogen 
into  water,  which  is  condensed  and  weighed.  These  operations 
are  conducted  according  to  the  processes  indicated  by  Liebig. 


ELEMENTARY   ANALYSIS.  407 

For  this  end,  the  organic  matter,  previously  dried  with  care,  is 
burned  with  an  excess  of  cupric  oxide.  The  operation  is  exe- 
cuted in  a  combustion-tube  of  hard  glass,  which  is  wrapped  with 
a  spiral  of  metallic  foil  to  prevent  it  from  bending  and  swell- 
ing under  the  influence  of  the  heat.  Well-dried  cupric  oxide 
is  introduced  into  the  tube,  then  an  intimate  mixture  of  the 
substance  to  be  analyzed  with  a  large  excess  of  the  same  oxide, 
and  the  remainder  of  the  tube  is  filled  with  pure  cupric  oxide. 

The  tube  is  then  placed  in  a  combustion  furnace,  and  its 
open  extremity  is  put  in  communication  with  (1)  an  U  tube,^ 
(Fig.  120),  containing  fragments  of  calcium  chloride  in  the  first 
branch,  and  pumice-stone  impregnated  with  sulphuric  acid  in 
the  second;  (2)  a  tube  with  five  bulbs,  h,  called  Liebig's  potash 
bulbs,  containing  a  concentrated  solution  of  potassium  hydrate, 
and  followed  by  a  small  U  tube,  i,  containing  pumice-stone  im- 
pregnated with  potassium  hydrate  in  the  first  branch,  and  frag- 
ments of  potassium  hydrate  in  the  second.  These  different 
tubes  have  first  been  accurately  weighed.  When  the  appa- 
ratus is  arranged,  the  combustion- tube  is  slowly  heated,  com- 
mencing at  the  extremity  B,  and  gradually  extending  the  heat 
so  that  each  part  of  the  tube  is  successively  heated  to  redness. 
The  water  formed  by  the  combustion  is  collected  in  the  first 
U  tube,  the  carbon  dioxide  is  absorbed  by  the  potassium  hy- 
drate in  the  bulbs.  When  the  operation  is  terminated,  the 
drawn-out  point  of  the  combustion-tube  is  broken,  and  con- 
nected by  means  of  a  caoutchouc  tube  with  a  gasometer  con- 
taining oxygen.  An  excess  of  the  latter  gas  is  then  passed 
through  the  combustion-tube,  in  order  to  drive  out  the  traces 
of  carbon  dioxide  and  aqueous  vapor  which  it  contains  at  the 
end  of  the  combustion.  It  is  then  only  necessary  to  weigh  the 
water  tube  and  the  carbon  dioxide  tubes.  The  increase  in 
weight  which  is  found  indicates,  on  one  hand,  the  quantity  of 
water,  and  on  the  other  the  quantity  of  carbon  dioxide,  pro- 
duced by  the  combustion  of  the  organic  matter.  The  compo- 
sition of  water  and  of  carbon  dioxide  being  known,  it  is  easy 
to  deduce  from  the  weight  of  these  two  bodies  the  quantities 
of  hydrogen  and  carbon  contained  in  the  analyzed  substance, 
and  consequently  the  proportion  of  these  two  elements  con- 
tained in  100  parts  of  that  substance. 

Fig.  120  represents  the  operation  towards  its  close :  the 
combustion-tube  is  in  the  gas-furnace,  B,  and  communicates, 
on  the  right  with  the  tubes  y,  h,  i,  destined  to  receive  the  pro- 


408 


ELEMENTS    OF    MODERN    CHEMISTRY. 


ELEMENTARY   ANALYSIS. 


409 


ducts  of  the  combustion,  on  the  left  with  two  large  U  tubes, 
the  first  of  which  is  filled  with  pumice-stone  impregnated  with 
potassium  hydrate  to  absorb  traces  of  carbon  dioxide,  the 
second  with  pumice-stone  saturated  with  sulphuric  acid  to 
absorb  moisture.  Through  these  tubes  is  passed  the  oxygen, 
at  the  close  of  the  operation,  to  expel  the  last  portions  of  carbon 
dioxide  and  vapor  of  water. 

When  the  substance  contains  carbon,  hydrogen,  and  oxygen, 
the  proportion  of  oxygen  is  the  difference  between  the  total 
percentage  of  carbon  and  hydrogen  found  and  100. 


.  121. 


Determination  of  Nitrogen,  —  Nitrogen  may  be  determined 
by  two  processes.  The  first  consists  in  burning  a  given  weight 
of  the  nitrogenized  substance  with  an  excess  of  cupric  oxide. 
The  carbon  of  the  substance  is  converted  into  carbon  dioxide  ; 
the  hydrogen  is  converted  into  water  ;  the  nitrogen  is  disen- 
gaged. The  gases,  nitrogen  and  carbon  dioxide,  are  received 
in  a  graduated  jar  standing  on  the  mercury-trough  and  con- 
taining potassium  hydrate.  The  carbon  dioxide  is  absorbed, 
the  nitrogen  remains.  At  the  close  of  the  operation,  the  last 
traces  of  nitrogen  are  expelled  by  a  current  of  carbon  dioxide. 
The  volume  of  nitrogen  is  then  measured^  and  its  weight  de- 
duced from  its  volume  (Dumas). 

The  second  process  (Fig.  121)  consists  in  decomposing  the 
nitrogenized  organic  matter  with  an  alkali  at  a  high  tempera- 
s  35 


410  ELEMENTS   OF   MODERN   CHEMISTRY. 

ture.  By  this  means  all  of  the  nitrogen  is  converted  into 
ammonia.  The  substance  is  intimately  mixed  with  soda  lime, 
that  is,  lime  impregnated  with  caustic  soda.  The  mixture  is 
heated  to  redness  in  a  tube  of  hard  glass,  and  the  ammonia  is 
received  in  a  tube  with  three  bulbs  containing  dilute  hydro- 
chloric acid.  Ammonium  chloride  is  formed ;  when  the  opera- 
tion is  terminated,  the  liquid  containing  the  salt  is  mixed  with 
a  solution  of  platinic  chloride.  It  is  then  evaporated  and 
exhausted  with  alcohol,  which  leaves  the  platinum  and  ammo- 
nium double  chloride,  2(NH4C1)  -f  PtCl4.  The  latter  is  col- 
lected upon  a  tared  filter,  then  washed  and  dried.  From  its 
weight  is  calculated  that  of  the  nitrogen  contained  in  the 
organic  substance  (Will  and  Varrentrapp). 

The  ammonia  disengaged  may  also  be  received  in  10  cubic 
centimetres  of  a  normal  solution  of  sulphuric  acid,  that  is,  an 
acid  liquor  containing  a  known  quantity  of  sulphuric  acid  in 
a  determined  volume. 

The  strength  of  this  acid  is  determined  by  neutralizing  10 
c.c.  of  it  with  a  dilute  alkaline  solution  of  known  strength  and 
noting  the  volume  of  the  latter  required.  The  same  operation 
is  repeated  with  the  10  c.c.  of  which  the  acid  has  been  par- 
tially neutralized  by  the  ammonia.  The  quantity  of  ammonia 
corresponds  to  the  difference  between  the  volumes  of  the  alka- 
line liquid  employed  in  these  two  operations,  and  can  easily  be 
calculated  by  simple  proportion  (Peligot). 

Determination  of  the  Molecular  Weight  of  Organic  Sub- 
stances.— Elementary  analysis  permits  the  determination  of 
the  centesimal  composition  of  organic  substances.  This  is 
indispensable,  but  it  is  insufficient  for  the  establishment  of 
their  atomic  composition,  that  is,  the  number  of  atoms  of  car- 
bon, hydrogen,  oxygen,  and  nitrogen  which  are  contained  in  a 
single  molecule  of  a  given  organic  compound.  But  if  the 
weight  of  the  molecule  be  known  (hydrogen  being  taken  as 
unity),  it  is  easy  to  deduce  the  atomic  composition  from  the 
figures  given  by  elementary  analysis,  as  will  be  seen  by  the 
following  example.  By  elementary  analysis  it  is  found  that 
100  parts  of  acetic  acid  contain 

Carbon 40. 

Hydrogen 6.67 

Oxygen .     53.33 

100JOO 

On  the  other  hand,  methods  which  will  be  described  have 


ELEMENTARY   ANALYSIS.  411 

shown  that  the  molecular  weight  of  acetic  acid  is  60  ;  that  is  to 
say,  the  total  weight  of  the  atoms  of  carbon,  hydrogen,  and 
oxygen  contained  in  a  molecule  of  acetic  acid,  is  60. 
Hence  by  the  following  proportions  : 

If  100  parts  acetic  acid  contain  40       of  carbon,      60  parts  contain  x. 
"  "  "  6.67  of  hydrogen,    "  "         y. 

"  «  "         53.33  of  oxygen         "  "          z. 

From  which,  x  =  24 ;  y  =  4 ;  z  =  32. 
Hence  24  represents  the  weight  of  the  atoms  of  C  contained  in  a  molecule 

of  acetic  acid. 
4  represents  the  weight  of  the  atoms  of  H  contained  in  a  molecule  of  acetic 

acid. 

32  represents  the  weight  of  the  atoms  of  0  contained  in  a  molecule  of  acetic 
acid. 

By  dividing  these  numbers  by  the  weights  of  the  respective 
atoms,  the  number  of  atoms  of  C,  H,  and  O  contained  in  a 
molecule  of  acetic  acid  is  readily  determined. 

24  -s-  12  =  2  atoms  of  carbon. 
4-s-l=4      "  hydrogen. 

32-5-16  =  2      "  oxygen. 

Hence  the  formula  of  acetic  acid  is  C2H*0*. 

After  the  analysis  of  an  organic  substance  has  been  made,  it 
is  only  necessary  to  determine  its  molecular  weight  in  order  to 
establish  its  atomic  composition.  Several  processes  are  em- 
ployed for  this  determination,  of  which  the  most  sure  is  the 
determination  of  the  vapor  density. 

We  know  that  if  one  atom  of  hydrogen  occupy  one  volume, 
the  molecules  of  organic  substances  occupy  two  volumes.  To 
find  the  weights  of  these  molecules  it  is  then  sufficient  to  deter- 
mine their  vapor  densities  compared  to  hydrogen ;  that  is,  to 
find  the  weight  of  one  volume  of  their  vapors,  that  of  one 
volume  of  H  being  taken  as  unity.  The  number  found  mul- 
tiplied by  2  gives  the  weight  of  two  volumes,  that  is,  the  weight 
of  the  molecule. 

Hence  a  simple  determination  of  the  vapor  density  is  suf- 
ficient for  the  establishment  of  the  molecular  weight.  Ordi- 
narily these  vapor  densities  are  given  as  compared  with  air 
taken  as  unity.  To  bring  them  to  the  hydrogen  scale  it  is 
then  only  necessary  to  multiply  them  by  14.44,  which  is  the 
exact  relation  of  the  density  of  air  to  that  of  hydrogen.  Thus 
the  vapor  density  of  acetic  acid,  determined  at  295°,  has  been 
found  equal  to  2.083  (Cahours).  This  number  multiplied  by 
14.44  gives  for  the  density  compared  to  hydrogen  30.08.  The 


412  ELEMENTS   OF   MODERN   CHEMISTRY. 

latter  number  expresses  the  weight  of  one  volume  of  acetic 
acid  vapor,  the  weight  of  one  volume  of  hydrogen  being  con- 
sidered as  1.  The  weight  of  two  volumes  of  this  vapor,  that 
is,  the  weight  of  the  molecule,  will  then  be  2  X  30.08  — 
60.16,  a  number  very  nearly  approaching  60,  the  theoretical 
molecular  weight. 

The  method  just  described  can  only  be  applied  to  substances 
which  can  be  volatilized  without  decomposition.  For  other 
bodies  another  method  must  be  adopted.  The  latter  consists 
in  forming  with  the  organic  body  definite  combinations,  the 
atomic  composition  of  which  may  be  known.  We  will  again 
consider  acetic  acid.  Salts  may  be  formed  with  this  acid,  and 
we  know  that  these  salts  contain  one  atom  of  metal.  We  may 
then  analyze  silver  acetate.  100  parts  of  that  salt  contain 
64.67  parts  of  silver.  This  fact  being  known,  it  is  easy  to  deter- 
mine the  molecular  weight  of  silver  acetate.  Since  the  latter 
contains  one  atom  of  silver,  we  can  conclude,  if  64.67  parts  of 
silver  are  contained  in  100  parts  of  silver  acetate,  108  parts 
of  silver,  that  is,  one  atom,  are  contained  in  x  parts  of  silver 
acetate ;  whence  x  =  167.  This  number  represents  the  molec- 
ular weight  of  silver  acetate.  That  of  acetic  acid  may  be  de- 
duced by  substituting  the  atomic  weight  of  hydrogen  for  that 
of  silver,  which  gives  for  the  molecular  weight  of  acetic  acid  60. 

Analogous  operations  and  reasoning  permit  the  determina- 
tion of  the  molecular  weights  of  bodies  playing  the  part  of 
bases.  They  are  combined  with  an  acid,  the  molecular  weight 
of  which  is  known,  and  the  composition  of-  the  combination 
furnishes  the  data  for  the  calculation  of  the  molecular  weight 
of  the  base.  This  method  can  be  applied  in  a  large  number 
of  analogous  cases,  and  presents  a  great  generality. 

ISOMERISM,  METAMERISM,  POLYMERISM. 

Elementary  analysis  demonstrates  that  many  bodies  which 
differ  in  their  physical  and  chemical  proparties,  possess  exactly 
the  same  centesimal  composition.  Such  bodies  are  said  to 
be  isomeric.  Two  kinds  of  isomerism  exist.  Sometimes  the 
isomeric  bodies  contain  the  same  number  of  similar  atoms  in 
molecules  of  the  same  size,  and  differ  only  by  the  arrange- 
ment of  these  atoms ;  sometimes  they  contain  similar  atoms 
united  in  the  same  proportion,  but  not  in  the  same  number,  in 
molecules  of  unequal  magnitude. 


ISOMERISM,  METAMERISM,  POLYMERISM.  413 

In  both  cases  the  centesimal  composition  is  the  same,  for  it 
depends  only  on  the  relative  number  of  the  atoms. 

The  first  kind  of  isomerism  constitutes  metamerism;  the 
second,  polymerism.  Acetic  acid  and  methyl  formate  are  an 
example  of  two  metameric  bodies.  Each  contains  2  atoms  of 
carbon,  4  of  hydrogen,  and  2  of  oxygen  ;  their  molecules  are 
equal  in  size,  but  diiferent  in  atomic  structure.  The  latter  fact 
may  be  expressed  by  the  following  formulae  : 

C2H3O.OH  acetic  acid 
CH3O.OCH  methyl  formate 

The  first  expresses  that  acetic  acid  contains  a  group  of  atoms, 
C2H30,  acetyl,  which  is  united  with  hydroxyl,  OH  ;  the  second, 
that  methyl  formate  contains  a  group,  CHO,  formyl,  which  is 
united  with  oxymethyl,  CH30.  The  difference  in  the  atomic 
arrangement  becomes  evident,  if  the  preceding  formulae  be 
developed  in  the  graphic  manner. 

0-H  O-CH3 

I  I 


I  I 

CH3  H 

Acetic  acid.  Methyl  formate. 

By  adopting  the  theory  of  atomicity,  chemists  have  been 
enabled  to  discover  the  atomic  structure  of  a  great  number  of 
combinations,  as  we  have  seen  in  the  case  of  acetic  acid  and 
methyl  formate.  Such  considerations  are  of  great  importance 
for  the  interpretation  of  isomerism,  and  we  will  have  frequent 
occasion  to  refer  to  the  subject  in  the  course  of  this  work. 

Acetic  acid  and  glucose  or  grape-sugar  present  an  example 
of  polymerism.  Both  contain  the  atoms  of  carbon,  hydrogen, 
and  oxygen,  united  together  in  the  same  proportions,  but  the 
molecule  of  the  second  contains  three  times  as  many  of  each 
as  that  of  the  first. 

C2H*02  acetic  acid. 
3  X  C*HK)2  =  C«H1206  glucose. 

Among  the  more  important  and  better  known  cases  of  po- 
lymerism, may  be  mentioned  the  numerous  hydrocarbons  which 
present  the  centesimal  composition  of  ethylene  or  olefiant  gas, 
and  which  diifer  from  it  by  the  regularly  increasing  number  of 
their  atoms  of  carbon  and  hydrogen.  These  bodies  form  the 
following  homologous  series  : 

35* 


414  ELEMENTS   OF   MODERN   CHEMISTRY. 

C2H*  ethylene. 

C3H6  propylene. 

C4H8  butylene. 

C5H10  amylene. 

C6RU  hexylene. 

C?H"  heptylene. 

C8Hi«  octylene,  etc. 

It  will  be  seen  that  butylene  contains  twice  as  many  carbon 
and  hydrogen  atoms  as  ethylene,  hexylene  contains  three  times 
as  many,  etc. 


FUNCTIONS  OF   OKGANIC   COMPOUNDS. 

In  the  study  of  mineral  chemistry  it  has  been  seen  that 
bodies  present  great  differences  in  properties,  according  to  their 
composition.  Some  are  simple  and  apt  to  enter  into  combina- 
tion ;  others  are  compound  and  indifferent ;  the  first  are  more 
or  less  energetic  in  their  affinities,  the  others  saturated  and 
satisfied.  In  one  case,  we  have  examined  either  more  or  less 
powerful  acids  or  bases,  some  of  which  are  hydrated,  as  potassa 
and  soda,  others  anhydrous,  as  the  oxides  of  lead  and  silver. 
In  the  other  case,  we  have  studied  the  salts  resulting  from  the 
union  of  the  former  bodies. 

In  organic  chemistry  we  again  encounter  various  kinds  of 
bodies  which  have  different  functions,  according  to  their  com- 
position. 

It  may  be  said,  in  a  general  manner,  that  the  properties  of 
compound  bodies  depend  upon  the  nature  of  the  atoms  and 
their  arrangement  in  the  molecule.  In  treating  of  isomerism, 
the  influence  of  the  latter  condition  has  been  indicated ;  that 
of  the  former  is  still  more  powerful. 

Water  and  potassium  hydrate  are  both  constituted,  and  in 
an  analogous  manner,  of  three  elementary  atoms.  Each  con- 
tains one  atom  of  oxygen  united  to  two  monatomic  atoms. 

HOH  KOH 

Water.  Potassium  hydrate. 

But  what  a  difference  in  their  properties !  But  may  not 
this  be  expected  when  it  is  considered  that  one  contains  the 
energetic  metal  potassium,  in  the  place  occupied  in  the  other 
by  the  light  gas  hydrogen  ?  Is  the  difference  between  potassa 
and  water  greater  than  that  between  potassium  and  hydrogen  ? 


MON ATOMIC   COMPOUNDS.  415 

And  if  for  the  two  atoms  of  hydrogen  we  substitute  two  atoms 
of  chlorine,  is  it  not  to  be  expected  that  hypochlorous  oxide 

C1-0-C1 

the  molecule  of  which  is  similar  in  structure  to  that  of  water, 
shall  differ  from  the  latter  in  its  properties  as  much  as  chlo- 
rine differs  from  hydrogen  ?  It  is  thus  that  the  nature  of  the 
elements  contained  in  compound  bodies  is  the  dominant  condi- 
tion in  the  manifestation  of  their  properties. 

The  following  considerations  are  of  a  nature  to  demonstrate 
the  truth  of  this  proposition  inasmuch  as  concerns  organic 
compounds : 

MONATOMIC   COMPOUNDS. 

Saturated  Hydrocarbons. — The  hydrocarbons  belonging 
to  the  series  of  marsh  gas  are  all  saturated.  Consider,  for 
example,  C2H6 ;  all  of  the  atomicities  of  two  atoms  of  carbon 
are  satisfied  by  the  union  of  the  latter  together  and  with  six 
atoms  of  hydrogen. 

HH 

H-C-C-H 

i    i 
H  H 

Ethane,  or  ethyl  hydride. 

It  is  the  same  with  all  of  its  homologues ;  the  hydrides  of 
propyl,  butyl,  amyl,  etc.,  are  all  saturated  hydrocarbons,  as  will 
be  seen  by  developing  the  formula  of  any  one  of  them,  pentane, 
for  example : 

HHHHH 

i     I     I     I     i 
H-C-C-C-C-C-H 

i     i    i    i    i 
HHHHH 

Pentane,  or  amyl  hydride. 

All  of  these  bodies  are  incapable  of  fixing  other  elements 
by  direct  addition,  but  they  may  be  modified  by  substitution, 
that  is,  one  or  several  of  their  atoms  of  hydrogen  may  be 
replaced  by  other  elements. 

Mpnatomic  Chlorides,  Bromides,  and  Iodides. — By  the 
reaction  of  bromine  upon  any  of  the  hydrocarbons,  we  may 


416  ELEMENTS   OF   MODERN   CHEMISTRY. 

obtain  compounds  containing  an  atom  of  bromine  in  the  place 
of  an  atom  of  hydrogen. 

C2H6     -f     Br2     =     C2H5Br     -f-     HBr 

Ethane.  Ethyl  bromide. 

A  saturated  and  indifferent  hydrocarbon  is  thus  converted 
into  a  bromide. 

The  corresponding  chloride  and  iodide  exist,  possessing  the 
same  constitution  as  the  primitive  hydrocarbon,  and  forming 
with  it  the  following  series : 

C2H6      ethane. 
C2H&C1  ethyl  chloride. 
C2H5Br  ethyl  bromide. 
C»H5I     ethyl  iodide. 

To  the  other  hydrocarbons  correspond  chlorides,  bromides, 
and  iodides  analogous  to  the  preceding.  Thus,  the  following 
groups  are  known : 

CH*      methane.  C5H12      pentane. 

CH3C1  methyl  chloride.  C5HnCl  amyl  chloride. 

CH3Br  methyl  bromide.  C5HUBr  amyl  bromide. 

CH3I    methyl  iodide.  C5HUI    amyl  iodide. 

All  of  these  bodies  may  be  made  to  undergo  the  most  varied 
transformations.  They  may  be  attacked  by  a  number  of  re- 
agents, to  which  they  present  a  hold,  as  it  were,  since  the  chlo- 
rine, bromine,  and  iodine  which  they  contain  are  gifted  with 
powerful  affinities. 

The  residues  resulting  from  the  subtraction  of  the  chlorine, 
bromine,  or  iodine  then  enter  into  other  combinations.  It  will 
be  remarked  that  these  residues  represent  the  saturated  hydro- 
carbons from  which  one  atom  of  hydrogen  has  been  removed. 

CH3    =CH3Br    —  Br,  orCH4    —  H 
=  c2H5Br  —  Br,  or  C2H6  —  H 
11  =  C5HnBr  —  Br,  or  C5H12  —  H 

The  atoms  of  carbon  contained  in  these  residues,  CH3,  C2H5, 
and  C5Hn,  are  no  longer  entirely  saturated,  since  Cl,  Br,  I,  or 
H  has  been  removed,  elements  which  saturated  one  atomicity. 
Therefore,  these  residues  are  capable  of  entering  other  com- 
binations, but  as  they  possess  only  one  free  atomicity,  they  can 
only  saturate  one  when  they  combine.  This  is  expressed  by 
saying  that  they  play  the  part  of  monatomic  radicals.  The 
chlorides,  bromides,  and  iodides  from  which  they  are  derived 
are  themselves  monatomic. 


MONATOMIC   COMPOUNDS.  41t 

Alcohols. — The  neutral  organic  hydrates  corresponding  to 
the  preceding  chlorides,  bromides,  and  iodides,  are  called 
alcohols. 

If  ethyl  iodide  be  heated  for  a  sufficiently  long  time  with 
potassium  hydrate,  potassium  iodide  will  be  formed,  and  the 
alkaline  liquid  will  contain  alcohol  which  may  be  separated. 

This  body  is  ethyl  hydrate  and  is  formed  according  to  the 
following  reaction : 

Cm5!     +     KOH    =    KI     +     C2H5.OH 

Ethyl  iodide.  Ethyl  hydrate. 

It  is  formed,  as  is  seen,  by  double  decomposition.  The 
potassium  having  removed  the  iodine  from  the  ethyl  iodide, 
the  monatomic  residue  C2H5  combines  with  the  monatomic 
residue  OH.  Alcohol  is  then  the  hydrate  which  corresponds 
to  the  iodide,  C2H5I,  and  to  the  hydrocarbon,  C2H6.  Analo- 
gous hydrates  correspond  to  the  other  hydrocarbons  of  the 
same  series ;  they  constitute  the  series  of  monatomic  alcohols, 
and  may  be  denned  as  derived  from  the  saturated  hydrocarbons 
by  the  substitution  of  the  group  hydroxyl  for  one  atom  of 
hydrogen.  The  alcohols  now  known  are  numerous  ;  the  follow- 
ing are  some  of  them: 

CIROII  methyl  hydrate,  or  methylic  alcohol. 
C*H5.OH  ethyl  hydrate,  or  ethylic  alcohol. 
C3H7.OH  propyl  hydrate,  or  propylic  alcohol. 
C*H9.OH  butyl  hydrate,  or  butylic  alcohol. 
C5HU.OH  amyl  hydrate,  or  amylic  alcohol. 
C6H13.OH  hexyl  hydrate,  or  hexylic  alcohol. 
C7H15.OH  heptyl  hydrate,  or  heptylic  alcohol. 
C8H17.OH  octyl  hydrate,  or  octylic  alcohol. 

Each  member  of  this  series  differs  from  that  which  follows 
by  — CH2.  All  are  allied  by  analogous  properties.  These  two 
conditions  characterize  homologous  bodies.  The  alcohols  of 
which  the  general  formula  is  CnH2n+1OH,  form  one  of  the  most 
important  series  of  homologues. 

If  one  of  these  alcohols  be  heated  with  hydrochloric,  hydro- 
bromic,  or  hydriodic  acid,  water  will  be  formed  and  the  alcohol 
will  be  converted  into  a  monatomic  chloride,  bromide,  or  iodide. 
In  this  reaction  the  hydroxyl,  OH,  is  replaced  by  chlorine, 
bromine,  or  iodine. 

C2H5.OH     +     HC1    =    H20     +     C2H5C1 

Ethyl  hydrate.  Ethyl  chloride. 

The  bodies  thus  formed  are  the  monatomic  chlorides,  bro- 

8* 


418  ELEMENTS   OP   MODERN   CHEMISTRY. 

mides,  or  iodides  before  considered.  These  experiments  expose 
the  relations  which  exist  between  the  latter  compounds  and  the 
corresponding  hydrates,  which  are  the  alcohols. 

Monobasic  Acids. — Acetic  acid,  which  exists  in  vinegar,  is 
a  derivative  of  alcohol,  of  which  it  is  one  of  the  products  of 
oxidation.  It  is  formed  under  many  conditions,  one  of  which 
is  the  oxidation  of  alcohol  vapor  on  contact  with  platinum 
black  and  the  air. 

C2H5.OH     -+     O3    =     C2H3O.OH     +     H20 

Alcohol.  Acetic  acid. 

In  this  reaction  an  atom  of  oxygen  removes  two  atoms  of 
hydrogen  to  form  water,  and  the  place  of  these  two  atoms  of 
hydrogen  is  filled  by  another  atom  of  oxygen.  The  group 
ethyl,  C2H5,  thus  becomes  the  group  acetyl,  C2H30,  and  if 
alcohol  be  the  hydrate  of  ethyl,  acetic  acid  is  the  hydrate  of 
acetyl.  We  can  account  for  this  reaction  by  developing  the 
formulae  of  alcohol  and  acetic  acid  according  to  the  principles 
before  explained. 

HH  HO 

H-C-C-OH     -f     0«    =     H-C-C-OH     -f     H2O 
i     I  i 

HH  H 

Alcohol.  Acetic  acid. 

In  alcohol,  the  second  carbon  atom  is  combined  with  two 
atoms  of  hydrogen  and  with  one  group  hydroxyl,  while  in 
acetic  acid  it  is  combined  with  an  atom  of  oxygen  and  a  group 
hydroxyl. 

Acetic  acid  contains  two  atoms  of  carbon  united  together, 
and  combined,  the  one  with  H3,  the  second  with  0  and  OH. 
It  is  thus  formed  of  a  group  CH3  united  to  a  group  CO-OH 
=  C02H.  There  exist  many  other  acids  analogous  to  acetic 
acid,  and  derived,  like  it,  by  oxidation  of  the  monatomic  alco- 
hols of  the  series  CnH2n+1OH.  All  of  these  acids  contain 
a  hydrocarbon  group  analogous  to  methyl,  combined  with  the 
group  C02H  =  CO-OH.  The  hydrogen  of  the  latter  group 
can  be  readily  replaced  by  an  equivalent  quantity  of  metal. 
This  hydrogen  is  said  to  be  strongly  basic,  and  all  of  the  organic 
acids  which  contain  a  single  group,  C02H,  united  to  a  hydro- 
carbon group,  are  monobasic  like  acetic  acid.  The  homologues 
of  the  latter  form  the  following  series : 


MONATOMIC   COMPOUNDS.  419 

C   H2  02  ==      H   -CQ2H  formic  acid. 
C2  H*  O2  =  C  H3  -C02H  acetic  acid. 


C3  H6  O2  ==  C2H5  -C02H  propionic  acid. 
C*  H8  O2  =  C3U7  -C02H  butyric  acid. 
C5  HK>02  =  C4H»  -C02H  valeric  acid. 
C6  H1202  =  C5H11-C02H  caproic  acid. 
C7  H"02  =  C6H13-C02H  oenanthic  acid. 
C8  H1602  =  C7H15-C02H  caprylic  acid. 
C9  H1802  =  C8H17-C02H  pelargonic  acid. 
CiOflMQ2  =  C»Hi»-C02H  capric  acid,  etc. 

The  first  series  of  formulae  indicates  simply  the  nature  and 
number  of  atoms  contained  in  the  acids  of  the  series  CnH2n02. 
They  are  empirical  formulae.  The  second  series  gives  certain 
indications  upon  the  relations  existing  between  these  atoms. 
They  are  rational  formulae,  and  when  developed  so  as  to  ex- 
press the  relations  between  all  of  the  atoms,  they  become 
constitutional  formulae. 

Compound  Ethers. — The  compound  ethers  are  combina- 
tions which  represent  acids  of  which  the  hydrogen  has  been 
replaced  by  an  alcoholic  group. 

If  one  of  the  alcohols  of  the  preceding  series,  ordinary  alco- 
hol, for  example,  be  heated  for  a  long  time  with  acetic  acid, 
water  will  be  formed,  and  a  volatile,  neutral  liquid  possessing  an 
agreeable  odor  may  be  separated  from  the  product ;  this  sub- 
stance is  ethyl  acetate,  or  acetic  ether.  It  is  formed  according 
to  the  following  reaction : 

C2H5.OH  +  C2H3O.OH  =  C2H50(C2H30)  +  H20 

Alcohol.  Acetic  acid.  Ethyl  acetate. 

On  comparing  this  compound  with  alcohol,  we  find  that  it 
is  formed  by  substitution  of  the  group  C2H30,  the  existence  of 
which  is  admitted  in  acetic  acid,  and  which  is  called  acetyl, 
for  one  atom  of  hydrogen  in  alcohol ;  and  this  atom  of  hydro- 
gen which  is  replaceable  by  acetyl  is  that  which  is  united  to  the 
oxygen  in  alcohol, — that  which  forms  a  part  of  the  hydroxyl 
group.  The  other  atoms  of  hydrogen,  those  which  constitute 
part  of  the  group  C2H5,  cannot  be  replaced  by  acetyl. 

All  of  the  acids  can  form  with  alcohol,  and  indeed  with  all 
of  the  alcohols,  compounds  analogous  to  ethyl  acetate,  and 
these  combinations  are  called  compound  ethers.  The  property 
possessed  by  the  alcohols  of  etherifying  acids  is  general  and 
characteristic  of  this  class  of  compounds.  Alcohols  which 
require  for  etherification  but  a  single  molecule  of  an  acid  anal- 


420  ELEMENTS    OF   MODERN    CHEMISTRY. 

ogous  to  acetic  acid  are  called  monatomic.     Many  exist  which 
are  not  included  in  the  preceding  series. 

Aldehydes,  —  Acetic  acid  is  not  the  only  product  of  the 
oxidation  of  alcohol.  There  is  another  compound  interme- 
diate between  these  two  ;  it  results  from  the  action  of  a  single 
atom  of  oxygen  upon  the  molecule  of  alcohol,  which  thus  loses 
two  atoms  of  hydrogen  without  other  change.  The  new  com- 
pound is  aldehyde. 

C2H60  +  0  =  H20  -f  C2H40 

Alcohol.  Aldehyde. 

It  is  a  very  volatile  liquid  having  a  great  tendency  to  become 
oxidized  and  converted  into  acetic  acid.  It  forms  crystalline 
combinations  with  the  alkaline  acid-sulphites.  To  the  other 
alcohols  of  the  series  CnH2n+2O,  and  other  acids  of  the  series 
CnH2n02,  correspond  compounds  analogous  to  aldehyde  by  their 
composition  and  by  their  properties.  They  form  the  following 
series: 

C2H40          aldehyde  or  acetaldehyde. 
C3H60          propionic  aldehyde. 
C*H80          butyric  aldehyde. 

valeric  aldehyde,  etc. 


Acetones.  —  When  calcium  acetate  is  submitted  to  dry  distil- 
lation a  neutral,  volatile  liquid  is  obtained,  having  a  peculiar 
aromatic  odor,  and  known  by  the  name  acetone. 

Ca"ic2iro2  =  C3H6°  +   CaC°3 

Calcium  acetate.  Acetone.  Calcium  carbonate. 

To  the  other  acids  of  the  acetic  acid  series  correspond  bodies 
analogous  to  acetone,  and  forming  with  it  a  homologous  series. 
These  acetones  are  related  by  properties  and  composition  to  the 
aldehydes.  Like  the  latter,  they  form  crystalline  combinations 
with  the  alkaline  acid-sulphites.  It  may  be  considered  that 
while  aldehyde  is  the  hydride  of  acetyl,  acetone  is  the  methyl- 
ide  of  acetyl,  and  that  in  general  the  acetones  are  derived  by 
the  substitution  of  an  alcoholic  group,  analogous  to  methyl,  for 
an  atom  of  hydrogen  in  the  aldehydes  considered  as  hydrides. 

CH3-CO-H  CH3-CO-CH3 

Aldehyde  (acetyl  hydride).  Acetone  (acetyl  methylide). 

Hence,  acetone  contains  two  methyl  groups  united  to  a  group, 
CO  (carbonyl).  Its  mode  of  formation  justifies  this  conclusion, 


MONATOMIC   COMPOUNDS.  421 

as  shown  in  the  following  equation,  in  which  the  constitutional 
formula  of  acetic  acid  is  employed : 

CH'IcOO>Ca    =     Ca"C°3     +     CH3-CO-CH* 

Calcium  acetate.  Calcium  carbonate.  Acetone. 

Chlorides  of  Acid  Radicals. — In  the  preceding  compounds 
we  have  admitted  the  existence  of  a  group,  C2H30  =  CH3-CO, 
existing  in  combination  with  OH  in  acetic  acid,  C2H3O.OH, 
with  hydrogen  in  aldehyde,  C2H3O.H,  and  with  methyl  in  ace- 
tone, C2H3O.CH3.  A  compound  is  known  in  which  this  same 
group  is  united  with  chlorine.  Acetyl  chloride,  C2H3O.C1,  is 
a  monatomic  chloride,  like  ethyl  chloride,  C2H5C1,  from  which 
it  is  distinguished  by  the  strongly  electro-negative  nature  of 
its  radical. 

If  acetyl  chloride  be  poured  into  water,  it  disappears  in  a 
short  time  with  development  of  heat  and  the  formation  of  acetic 
and  hydrochloric  acids. 

C2H3O.C1     +     H20    =     CTFO.OH     +     HC1 

Acetyl  chloride.  Acetic  acid. 

To  acetyl  chloride  correspond  other  chlorides  which  contain 
radicals  of  acids  analogous  to  acetic  acid.  When  they  are 
treated  with  water  they  yield  hydrochloric  acid  and  the  acids 
corresponding  to  their  radicals. 

C3H5O.C1  C3H5O.OH 

Propionyl  chloride.  Propionic  acid. 

C4H7O.C1  C4H7O.OH 

Butyryl  chloride.  Butyric  acid. 

C7H5O.C1  C7H5O.OH 

Benzoyl  chloride.  Benzoic  acid. 

Amides. — If  acetyl  chloride  be  treated  with  ammonia,  am- 
monium chloride  will  be  formed,  together  with  a  solid,  neutral, 
nitrogenized  body  called  acetamide. 

C2H5O.C1  +  2NH3  =  NH4C1  +  C2H3O.NH2 

Acetyl  chloride.  Acetamide. 

There  are  many  other  compounds  similar  to  acetamide,  and 
known  by  the  name  amides.  They  are  formed  by  the  action 
of  ammonia  upon  organic  chlorides  analogous  to  acetyl  chloride. 
They  are  also  formed  by  the  action  of  heat  upon  the  ammo- 
niacal  salts  of  the  monobasic  acids.  The  latter  compounds 
then  lose  one  molecule  of  water,  and  are  converted  into  amides. 
C5H9O.ONH4  =  C5H9O.NH2  +  H20 

Ammonium  valerate.  Valeramide. 

36 


422  ELEMENTS   OF   MODERN   CHEMISTRY. 

Acetamide  may  be  regarded  as  ammonia  in  which  an  atom 
of  hydrogen  has  been  replaced  by  the  radical  acetyl. 

(  H  (  C2H30  f  C5H90 

NfH  N^H  N^H 

(H  (H  (H 

Ammonia.  Acetamide.  Valeramide. 

Compound  Ammonias,  or  Amines.  —  If  ethyl  iodide  be 
heated  with  ammonia,  one  of  the  products  of  the  reaction  will 
be  the  hydriodide  of  a  base  derived  from  ammonia  by  the  sub- 
stitution of  an  ethyl  group  for  an  atom  of  hydrogen. 

C2H5I     +     NH3    =     (C2H5)NH2.HI 

Ethyl  iodide.  Ethylamine  hydriodide. 

In  this  reaction,  other  ethylated  bases  are  formed,  independ- 
ently of  ethylamine,  among  which  must  be  mentioned  diethyl- 
amine  and  triethylamine.  All  present  the  most  striking  anal- 
ogy to  ammonia.  They  may  be  regarded  as  ammonia  in  which 
one,  two,  or  three  atoms  of  hydrogen  have  been  replaced  by 
one,  two,  or  three  ethyl  groups. 


H)  C2H5)  C2H5)  C2H5) 

H  V-  N  H  t  N          C2H5  I  N         C2H5  (•  N 

H  \  H  )  H  )  C2H5  ) 

Ammonia.  Ethylamine.  Diethylamine.         Triethylamine. 

The  other  alcoholic  groups,  CnH2n+1,  can  in  the  same  man- 
ner replace  one  or  more  atoms  of  hydrogen  in  ammonia.  The 
results  are  bases  having  constitutions  analogous  to  those  of  the 
ethyl  bases.  They  are  called  amines,  or  compound  ammonias. 

It  is  necessary  that  the  signification  of  the  formulae  above 
given  and  those  that  are  to  follow  shall  be  clearly  understood. 
They  are  examples  of  typical  notation,  and  indicate  the  rela- 
tions of  the  compounds  with  the  type  ammonia. 

(H 

N'"  1  H 
(H 

The  brace  joining  the  three  hydrogen  atoms  signifies  that 
the  whole  three  are  united  to  a  single  atom  of  triatomic  nitro- 
gen, with  which  each  exchanges  one  atomicity;  this  may  be 
expressed  by  writing  the  formula  for  ammonia  thus  : 


MONATOMIC   COMPOUNDS.  423 

What,  then,  takes  place  when  one  or  more  atoms  of  hydro- 
gen are  replaced  by  a  group  like  ethyl  ?  The  latter  exchanges 
one  atomicity  with  the  nitrogen  atom,  precisely  as  the  hydro- 
gen atom  did,  and  combines  with  the  nitrogen  by  one  of  the 
atoms  of  carbon  of  the  group  ethyl,  CH3-CH2,  which  requires 
the  satisfaction  of  one  atomicity. 

This  is  clearly  expressed  in  the  following  graphic  formulae : 
H  H 

N-CH2-CH3  N-CH2-CH3 

H  ilP-CH3 

Ethylamine.  Diethylamine. 

However,  such  formulae  would  be  too  cumbrous  for  ordinary 
use,  and  our  formulae  must  be  more  condensed. 

/WW  /C2H5 

N^H  N^C2H5  N(C2H5)3 

XH  XH 

Ethylamine.  Diethylamine.  Triethylamine. 

Phosphines. — Arsines. — Stibines. — There  exist  several  se- 
ries of  combinations  belonging  to  the  same  type  as  the  com- 
pound ammonias,  but  in  which  the  nitrogen  is  replaced  by 
phosphorus,  arsenic,  or  antimony.  These  compounds  are  de- 
rived from  the  hydrogen  compounds  of  phosphorus,  arsenic, 
and  antimony  by  the  substitution  of  one  or  more  alcoholic 
groups  for  one  or  more  atoms  of  hydrogen. 


H  }•  P  C2H5  V  P  C2H5 

H   )  H  )  C2H5 

Hydrogen  phosphide.  Ethylphosphine.  Diethylphosphine.  Trieth.vlphosphine. 

H)               CH3)  CH»)  CH3) 

HUs             H   (•  As  CH^As  CH3Us 

HJ                  H)  CTJ  CH3) 

Hydrogen  arsenide.    Methylarsine.  Dimethylarsine  Trimethylarsine. 

TT  -x  chloride. 
H 


H  [  Sb  C2H5  \  Sb 

H  )  C2H5  ) 

Hydrogen  antimonide.  Triethylstibine. 

Organo-metallic  Compounds.— Ethyl  and  its  congeneric 
compounds,  methyl,  amyl,  etc.,  can  enter  into  combination  not 
only  with  nitrogen,  phosphorus,  arsenic,  etc.,  of  which  they 
saturate  one  or  more  atomicities,  but  with  a  large  number  of 


424  ELEMENTS   OF   MODERN   CHEMISTRY. 

metals.     Thus,  zinc,  which  is  diatomic,  can  combine  with  two 
ethyl  groups  to  form  zinc  ethyl. 

7     (C2H5 

/n  {  C2H5 

Mercury,  also  diatomic,  can  unite  with  one  or  two  ethyl  or 
methyl  groups,  etc.  In  the  second  case,  the  new  combination 
is  saturated  ;  in  the  first,  it  is  monatomic,  (Hg"C2H5/,  and  re- 
quires for  saturation  an  atom  of  a  monatomic  element,  or  a 
monatomic  group,  iodine,  for  example. 


TT</' 
Hg 

Mercur-ethyl.  Mercur-monethyl  iodide. 

Bismuth,  which  is  triatomic,  can  fix  three  ethyl  groups. 

(  C2H5 

Bi'"  \  C2H5 

(C2H5 

Bismuth-ethyl. 

Stanno-tetrethyl  is  formed  by  the  union  of  four  ethyl  groups 
with  one  atom  of  tetratomic  tin. 

f  C2H5 

SnJ  C2H* 

fen  1  C2H5 

[  C2H5 

If  the  four  atomicities  of  tin  be  not  all  satisfied,  non-satu- 
rated compounds  may  be  formed. 


( 
Sn"  \         ,  r&Fl  C2H5  or 

(  C2H5  C2H5 

Stanno-diethyl.  Stanno-triethyl. 

Stanno-diethyl  is  known  in  the  free  state,  but  stanno-triethyl 
doubles  its  molecule  as  soon  as  it  is  set  at  liberty,  combining 
with  itself,  as  it  can  combine  with  iodine. 

ISn"(C2H5)3          (C2H5)3Sniv-Sn-(C2H5)3  =  Sn2(C2H5)6. 

Stanrio-triethyl  iodide.  Sesquistarinethyl. 

Non-saturated  compounds  are  apt  to  combine  with  other 
elements  or  radicals.  Stanno-tetrethyl,  which  is  saturated,  does 
not  possess  this  faculty. 

The  bodies  just  mentioned  belong  to  the  class  of  organo- 
metallic  compounds.  Their  study  is  of  great  importance  in 
the  history  of  the  atomicity  of  the  metals,  that  is,  their  power 
of  saturation.  The  theoretical  considerations  concerning  them 
have  been  discussed  by  Frankland,  Baeyer,  and  Cahours. 


MONATOMIC   RADICALS.  425 

Monatomic  Radicals. — From  the  preceding  summary  may 
be  understood  the  position  occupied  in  organic  chemistry  by 
certain  groups  containing  carbon,  groups  that  are  distinguished 
as  monatomic  because  they  can  manifest  but  a  single  atomicity. 
Only  a  single  monatomic  atom  or  group  is  wanting  that  all  of 
the  carbon  atoms  contained  in  these  groups  may  be  entirely 
saturated.  These  groups  of  atoms  or  radicals  cannot  exist  in 
the  state  of  liberty,  but  they  can  pass  from  one  compound  to 
another,  replacing  a  single  atom  of  hydrogen  or  other  mon- 
atomic element,  and  consequently  playing  the  part  of  that  ele- 
ment in  the  new  combination.  This  is  expressed  by  saying 
that  these  groups  act  as  monatomic  radicals. 

To  indicate  the  constitution  of  the  combinations  containing 
such  groups,  and  especially  the  metamorphoses  tha'o  they  may 
undergo  by  exchanging  these  radicals  by  double  decomposition, 
it  is  convenient  to  distinguish  the  latter  by  unique  expressions, 
occupying  a  place  in  the  formula  distinct  from  that  of  the 
other  elements.  The  composition  of  all  of  the  bodies  which 
have  just  been  reviewed  may  be  represented  by  very  simple 
formulae,  by  comparing  them  to  hydrogen  compounds,  such  as 
free  hydrogen,  or  hydrochloric  acid,  water,  and  ammonia.  The 
notation  then  assumes  a  typical  form,  exceedingly  clear  for  the 
interpretation  of  the  majority  of  reactions. 

The  following  are  the  typical  formulae  for  the  combinations 
that  have  been  considered : 


TYPE  HH.  TYPE  „  \  0.  TYPE 


H) 

HVN. 

Hj 


(C2H5)) 
(C2H5)C1  W"TI^O  H^N 


Ethyl  chloride.  Ethyl  hydrate.  Ethylamine. 


tya 

(C2H5 


(C2H30)C1  ^gJ  j  0  (C2H5)  \  N 

Acetyl  chloride.  Ethyl  oxide.  Diethylamine. 

(C2H30)H  (C2H30)  |  Q  (C2H5) 

(C2H5) 

Aldehyde.  Acetic  acid.  Triethylamine. 

/fi2TT3r^  *l  (C2H30)  ^ 

(C2H30)(CH3)          (\cw]  JO  H  C  N 

Acetone.  Ethyl  acetate.  Acetamide. 

36* 


426  ELEMENTS   OF   MODERN   CHEMISTRY. 


POLYATOMIC   COMPOUNDS. 

If  chlorine  and  olefiant  gas,  or  ethylene,  be  mixed  in  equal 
volumes,  both  gases  disappear  and  are  converted  into  an  oily 
substance,  which  was  formerly  called  Dutch  liquid.  This  body 
results  from  the  combination  of  a  molecule  of  ethylene  with  a 
molecule  (two  atoms)  of  chlorine.  It  is  ethylene  chloride. 

C2H4    +     CP    ==     C2H4CP 

Ethylene.  Ethylene  chloride. 

If  the  constitution  of  ethylene  gas,  C2H4,  be  compared  with 
that  of  the  saturated  hydrocarbon  ethane,  C2H6,  which  like  the 
former  contains  two  atoms  of  carbon,  it  will  be  noticed  that  it 
contains  two  atoms  of  hydrogen  less. 

_   JJ2   = 


In  ethylene  the  six  atomicities  of  the  pair  of  carbon  atoms 
are  not  saturated.  Hence  that  gas  can  absorb  directly  two 
atoms  of  chlorine,  bromine,  or  iodine  to  form  a  saturated  com- 
pound. 

HH  H   H  HH 

H-C-C-H  -C-C-  C1-C-C-C1 

ii  ii  ii 

HH  HH  HH 

Ethane.  Ethylene.  Ethylene  chloride. 

It  is  a  diatomic  radical,  and  it  can  exist  in  the  free  state 
because  until  other  atoms  are  presented  to  satisfy  the  atom- 
icities of  the  two  atoms  of  carbon,  those  two  atoms  are  bound 
together  by  a  double  affinity.  Thus,  H2C=CHa.  One  of 
these  bonds  is  loosed  when  the  ethylene  manifests  its  affinities 
and  enters  directly  into  combination,  because  the  affinity  of 
carbon  for  chlorine  or  such  an  element  is  greater  than  its 
affinity  for  carbon  Ethylene  is  the  first  of  a  numerous  class. 
The  following  bodies  form  with  it  the  homologous  series  CnH2n  : 

C2H*    ethylene. 
C3H6     propylene. 
C4H8    butylene. 
C5H10   amylene. 
C6H12   hexylene. 
C7H14   heptylene. 
C8H16   octylene. 
C9H18  nonylene. 
CioH20  decylene,  etc. 


POLYATOMIC   COMPOUNDS.  427 

All  of  these  bodies  are  able  to  fix  directly  two  atoms  of 
chlorine  or  bromine.  When  they  enter  into  combination,  they 
take  the  place  of  two  atoms  of  hydrogen.  They  can  pass  by 
double  decomposition  from  one  compound  to  another,  and  their 
combinations  may  undergo  various  metamorphoses  analogous 
to  those  already  indicated. 

Diatomic  Alcohols  or  Glycols.  —  The  glycols  are  compounds 
in  which  the  two  atomicities  of  the  diatomic  radicals  are  saturated 
by  two  hydroxyl  groups.  The  two  atoms  of  bromine  in  ethy- 
lene  bromide,  C2H4Br2,  may  be  replaced  by  two  hydroxyl  groups 
(OH),  and  the  resulting  combination  is  ethylene  dihydrate. 

<?H'<Br  C'H'<OH 

The  two  atoms  of  hydrogen  united  to  the  oxygen  in  the 
hydroxyl  groups  in  glycol  may  both  be  replaced  by  acid  radi- 
cals analogous  to  acetyl,  just  as  the  single  atom  of  hydrogen  in 
the  single  hydroxyl  group  of  a  monatomic  alcohol  may  be 
replaced  by  an  acid  radical.  This  is  characteristic  of  a  diatomic 
alcohol. 

To  ethylene  dihydrate,  or  ordinary  glycol,  correspond  the 
hydrates  of  the  other  hydrocarbons  homologous  with  ethylene. 
The  following  glycols  are  known  : 

C2H*{°,£  glycol. 
CWJggpropylglycol. 
™  butylglycol. 


{  {*H  hexylglycol,  etc. 

Around  each  of  these  bodies  are  grouped  a  great  number  of 
derivatives,  among  which  we  can  only  consider  the  ethers,  acids, 
and  compound  ammonias. 

Ethers  of  the  Glycols.  —  The  ethers  of  the  glycols  result 
from  the  substitution  of  alcoholic  or  acid  radicals  for  the  hydro- 
gen of  the  groups  OH.  One  or  both  of  these  hydrogens  may 
be  thus  replaced,  and  the  following  examples  will  illustrate  the 
constitution  of  the  compounds  so  formed  : 

r-2H4  I  O.C2H5  p2H4  f  O.C2H5  f  O.C2H30  p2TT4  f  0.0*11*0 

1   1  OH  *   1  O.C2H5  *   j  OH  *   1  O.C'H'O 

Monethylic  glycol.       Diethylic  glycol.        Glycol  monajetate.         Glycol  diacetate. 


428  ELEMENTS   OF   MODERN    CHEMISTRY. 

Diatomic  and  Dibasic  Acids.  —  Diatomic  acids  result  from 
the  oxidation  of  the  glycols.  Their  formation  and  constitu- 
tion may  be  understood  by  developing  the  formulae  of  the 
hydrocarbons  which  constitute  the  radicals  of  these  glycols. 
Ordinary  glycol  may  yield  two  acids  by  oxidation,  the  first 
resulting  from  the  substitution  of  an  atom  of  oxygen  for  two 
atoms  of  hydrogen,  the  second  from  the  substitution  of  two 
atoms  of  oxygen  for  four  atoms  of  hydrogen.  The  following 
formulae  express  the  constitution  and  derivation  of  these  com- 
pounds : 

CH2          CH2Br          CH2.OH      CH2.OH        CO.OH 
CH2          ilPBr          (W.OH      Ao.OH         (k).OH 

Ethylene.    Ethylene  bromide.          Glycol.          Glycollic  acid.          Oxalic  acid. 

Glycollic  and  oxalic  acids,  which  are  produced  by  the  oxida- 
tion of  glycol,  are  both  diatomic  because  they  are  both  derived 
from  a  diatomic  alcohol  ;  but  the  first  is  monobasic  because  it 
contains  but  a  single  atom  of  hydrogen  that  can  be  replaced  by 
a  metal.  The  second  is  dibasic,  for  it  contains  two  atoms  of 
hydrogen  that  are  replaceable  by  an  equivalent  quantity  of  metal. 
This  basic  hydrogen  is  that  which  forms  part  of  the  group 
C02H.  Oxalic  acid  is  composed  simply  of  two  groups  -C02H  ; 
it  is.  dibasic.  Glycollic  acid  contains  but  one,  and  it  is  conse- 
quently monobasic.  The  hydrogen  united  to  the  oxygen  in 
the  group  -CH2.OH  is  called  alcoholic  hydrogen  ;  it  may  be 
replaced  by  an  acid  radical,  but  it  cannot  be  easily  replaced  by 
a  metal.  All  bodies  containing  a  group  CH2.OH  are  alcohols, 
and  all  bodies  containing  a  group  CO.OH  are  acids.  The 
alcohols  and  acids  are  thus  defined  by  their  constitution.  Gly- 
collic acid  is  at  the  same  time  an  alcohol  and  an  acid,  for  it 
contains  both  a  group  CH2.OH  and  a  group  CO.OH. 

There  exists  a  series  of  acids  homologous  with  glycollic  acid, 
and  another  series  homologous  with  oxalic  acid.  Both  series 
appertain  to  the  superior  diatomic  alcohols. 

Diatomic  Ammonias  or  Diamines.  —  Compounds  exist 
which  hold  the  same  relation  to  the  diatomic  alcohols  as  ethyl- 
amine  and  its  homologues  to  the  monatomic  alcohols.  Such 
a  compound  is  ethylene-diamine.  Its  relations  with  ethylene 
chloride  and  glycol  are  expressed  by  the  following  formulae  : 


Ethylene  chloride.  Glycol.  Ethylene-diamine. 


CYANOGEN.  429 

Alcohols  of  Higher  Atomicity.  —  There  are  alcohols  of 
higher  atomicity  ;  glycerin,  for  example,  is  a  triatomic  alco- 
hol. It  contains  a  radical,  C3H5,  which  is  triatomic  since  it  is 
derived  from  the  saturated  hydrocarbon  C3H8,  by  the  subtrac- 
tion of  three  atoms  of  hydrogen.  Erythrite  is  a  tetratomic 
alcohol  ;  it  contains  the  tetratomic  radical  C4H6  =  C4H10  —  H4. 
Lastly,  the  sweet,  sugar-like  substance  derived  from  manna 
and  known  as  mannite  is  a  hexatomic  alcohol.  There  are 
numerous  similar  substances  which  are  alcohols  of  higher 
atomicity.  The  following  formulae  express  the  composition 
and  the  functions  of  these  polyatomic  alcohols  : 

OH 


C6H8*(OH)6 

OH 

Glycerin.  Erythrite.  Mannite. 

Around  these  bodies  are  grouped  the  numerous  correspond- 
ing derivatives,  ethers,  acids,  etc. 

It  will  be  seen  by  the  preceding  considerations  that  the  neu- 
tral hydrates,  called  alcohols,  are  highly  important  in  them- 
selves and  on  account  of  the  derivatives  which  attach  to  them. 
Hence  the  elements  of  a  natural  classification  of  organic  com- 
pounds are  deduced. 

COMPOUNDS  OF   CYANOGEN. 

Gay-Lussac  gave  the  name  cyanogen  to  the  radical  of  prussic 
or  hydrocyanic  acid,  which  was  discovered  by  Scheele  in  1782. 
This  radical  is  composed  of  one  atom  of  carbon  and  one  atom  of 
nitrogen.  In  hydrocyanic  acid  it  is  united  with  hydrogen  ;  in 
the  cyanides  it  is  combined  with  the  metals. 

H(CN)'  K(CN)'  Hg"(CN)2 

Hydrocyanic  acid.  Potassium  cyanide.  Mercury  cyanide. 

The  preceding  compounds  may  be  compared  with  the  corre- 
sponding chlorides  : 

HC1  KC1  HgCP 

Hydrochloric  acid.  Potassium  chloride.  Mercuric  chloride. 

It  is  somewhat  remarkable  that  potassium  cyanide  is  iso- 
morphous  with  potassium  chloride. 

In  the  preceding  compounds,  cyanogen,  which  is  composed  of 
an  atom  of  carbon  and  an  atom  of  nitrogen,  plays  a  part  anal- 
ogous to  that  of  chlorine.  It  is  a  monatomic  radical  ;  nitrogen, 


430        ELEMENTS  OF  MODERN  CHEMISTRY. 

which  is  triatomic,  can  saturate  only  three  of  the  four  atomici- 
ties which  reside  in  an  atom  of  carbon.  Hence  there  remains 
one  free  atomicity,  and  cyanogen  can  act  as  a  monatomic  radi- 
cal, -CEN. 

CYANOGEN. 

(CN)2  =  Cy2 

Preparation. — Mercury  cyanide  is  heated  in  a  small  retort 
fitted  with  a  delivery-tube.  The  mercury  volatilizes,  and  a  gas 
is  disengaged  which  may  be  collected  over  mercury.  There 
remains  in  the  retort  a  solid  brown  mass  which  possesses  the 
same  composition  as  cyanogen,  and  is  known  as  paracyanogen. 

Hg(CN)2  *=  (CN)2  -f  Hg. 

Composition  and  Properties. — Cyanogen  is  a  colorless  gas, 
possessing  a  strong  odor  of  bitter  almonds.  It  may  be  easily 
liquefied  by  a  pressure  of  4  atmospheres  or  a  temperature  of 
— 25°  Its  density  is  1.8064  compared  to  air,  or  26  compared 
to  hydrogen.  This  is  free  cyanogen. 

It  has  separated  from  the  mercury,  which  is  condensed  in 
little  drops  in  the  dome  of  the  retort.  The  atom  of  mercury 
was  combined  with  two  groups  (CN),  which  unite  together 
when  they  separate  from  the  mercury,  and  remain  combined 
together  in  the  gas  which  is  disengaged.  The  latter  contains 
CN  combined  with  CN.  Its  formula  is : 

NC-CN  =  (CN)2  =  Cy2 

2  volumes  of  this  gas  contain  two  atoms  of  carbon  and  two 
atoms  of  nitrogen. 

This  composition  may  be  demonstrated  by  eudiometric  analy- 
sis. 

2  volumes  of  cyanogen  and  4  volumes  of  oxygen  are  intro- 
duced into  a  mercury  eudiometer.  On  the  passage  of  an  electric 
spark  there  is  a  flash  of  blue  light,  and  the  volume  of  the  gas 
is  not  changed.  If  a  solution  of  potassium  hydrate  be  now 
passed  into  the  eudiometer,  the  six  volumes  of  gas  will  be 
reduced  to  two. 

4  volumes  of  CO2  are  formed; 

2  volumes  of  N  remain. 

2  volumes  of  cyanogen  then  contain  the  carbon  contained  in  2C02,  that 
is,  C2,  and  N2. 

This  is  expressed  by  saying  that  the  formula  of  cyanogen,  C2N2  =  Cy2, 
corresponds  to  2  volumes. 


HYDROCYANIC   ACID.  431 

On  contact  with  flame,  cyanogen  takes  fire  and  burns  in  the 
air  with  a  purple  flame,  yielding  carbon  dioxide  and  nitrogen. 

Water  dissolves  four  and  one-half  times  its  volume  of  cyan- 
ogen.    When  this  solution  is  left  to  itself  it  deposits  brown 
flakes.    It  then  contains  in  solution  urea,  ammonium  carbonate, 
ammonium  cyanide,  and  ammonium  oxalate. 
C2N2      +    4H20    =    (NH4)2C20* 

Cyanogen.  Ammonium  oxalate. 

C2N2      +     H20    =    HCN     +     °0*N 

Cyanogen.  Hydrocyanic  acid.      Cyanic  acid. 

C°jN   +     H'O    =     CO2      +     NH3 

Cyanic  acid.  Ammonia. 

The  ammonia  formed  by  the  latter  reaction  combines  with 
the  cyanic  acid  to  form  ammonium  cyanate,  which  becomes 
converted  into  urea,  as  will  be  seen  shortly. 

It  is  a  curious  fact  that  in  the  presence  of  a  small  quantity 
of  aldehyde,  the  decomposition  of  an  aqueous  solution  of 
cyanogen  yields,  almost  entirely,  but  one  product,  —  oxamide. 


Oxamide. 

If  a  fragment  of  potassium  be  heated  in  cyanogen  gas,  a 
brilliant  flash  of  light  takes  place  ;  in  combining  with  cyanogen 
potassium  becomes  incandescent.  Potassium  cyanide  is  formed. 
(CN)2  -f  K2  =  2KCN 

In  this  reaction,  cyanogen  combines  directly  with  a  metal. 
It  acts  as  a  simple  element,  such  as  chlorine. 

Paracyanogen,  which  has  been  mentioned  before,  is  a  poly- 
meride  of  cyanogen.  When  it  is  quickly  heated  to  redness,  it 
is  entirely  transformed  into  cyanogen  gas. 

HYDROCYANIC   ACID. 

(PRUSSIC   ACID.) 
HCN  =  HCy 

Preparation.  —  Gray-Lussac  prepared  hydrocyanic  acid  by 
heating  mercury  cyanide  with  hydrochloric  acid. 

An  easier  process  consists  in  decomposing  prussiate  of  potash 
(potassium  ferrocyanide)  with  sulphuric  acid.  8  parts  of  the 


432  ELEMENTS   OF    MODERN   CHEMISTRY. 

salt  in  fine  powder  are  heated  in  a  retort  with  9  parts  of  sul- 
phuric acid,  previously  diluted  with  14  parts  of  water. 

The  neck  of  the  retort  is  inclined  upwards,  so  that  the  aque- 
ous vapors  are  condensed  and  run  back  into  the  retort,  while 
the  vapor  of  prussic  acid,  which  is  very  volatile,  is  dried  by 
passage  through  a  tube  containing  calcium  chloride,  and  con- 
densed in  a  receiver  placed  in  a  freezing  mixture  of  ice  and 
salt. 

Properties. — This  acid  is  a  colorless,  limpid,  and  very  vol- 
atile liquid,  having  a  penetrating  odor  resembling  that  of  bitter 
almonds.  Its  density  at  7°  is  0,7058.  It  boils  at  26.5°,  and 
solidifies  to  a  crystalline  mass  at  — 15°. 

It  scarcely  reddens  blue  litmus-paper.  On  contact  with  an 
incandescent  body,  it  takes  fire  and  burns  with  a  white  flame 
lightly  tinted  with  violet. 

It  does  not  keep  long  in  the  pure  state.  It  becomes  brown, 
and  is  finally  converted  into  a  solid,  brown  mass. 

It  dissolves  in  water  in  all  proportions.  A  solution  contain- 
ing 2  per  cent,  is  used  in  medicine. 

When  hydrocyanic  acid  is  mixed  with  its  own  volume  of 
concentrated  hydrochloric  acid,  the  mixture  gets  hot  and  soon 
deposits  abundant  crystals  of  ammonium  chloride.  The  solu- 
tion contains  formic  acid. 

HCN    +     2H20    «    CH202     +     NH3 

Hydrocyanic  acid.  Formic  acid. 

In  reactions  with  the  hydracids,  hydrocyanic  acid  can  function 
like  a  compound  ammonia,  N(CH)'"  (formonitrile).  It  unites 
with  elevation  of  temperature  with  hydrochloric,  hydrobromic, 
and  hydriodic  acids  to  form  compounds,  such  as  N(CH)'". 
HC1  and  N(CH)'".HI,  that  may  be  compared  to  the  ammo- 
nium salts.  In  these  crystalline  compounds,  the  anhydrous 
bases  can  displace  the  hydrocyanic  acid,  as  they  displace  am- 
monia in  the  ammoniacal  salts  ;  thus, 

N(CH)HC1  +  NH8  =  NH4C1  +  HCN 

Cupric  oxide  displaces  hydrocyanic  acid  in  the  same  manner 
in  the  hydrobromide  of  formonitrile. 

The  oxidized  organic  acids  unite  only  with  difficulty  with 
hydrocyanic  acid,  and  at  an  elevated  temperature  (Arm. 
Gautier). 

"  Hydrocyanic  acid  is  one  of  the  most  rapid  and  most  danger- 
ous of  poisons.     A  single  drop  placed  upon  the  eye  of  a  rabbit 


METALLIC   CYANIDES.  433 

is  sufficient  to  kill  the  animal  in  a  few  instants,  and  after  vio- 
lent convulsions. 

Hydrocyanic  acid  may  be  detected  by  the  following  tests : 

1.  It  gives  a  white  precipitate  of  silver  cyanide  with  silver 
nitrate,  and  this  precipitate  does  not  darken  on  exposure  to 
light.     When  properly  dried  and  heated,  silver  cyanide  disen- 
gages cyanogen. 

2.  If  a  drop  of  hydrocyanic  acid  be  added  to  a  mixed  solu- 
tion of  ferrous  and  ferric  sulphates,  and  an  excess  of  potassium 
hydrate  be  added,  a  thick,  dark-colored  precipitate  is  formed. 
If  this  be  treated  with  an  excess  of  hydrochloric  acid,  the  fer- 
rous and  ferric  oxides  precipitated  will  be  dissolved,  and  Prus- 
sian blue  will  remain,  strongly  coloring  the  liquid. 

METALLIC   CYANIDES. 

We  will  only  consider  the  two  more  important  metallic  cya- 
nides, those  of  potassium  and  mercury. 

Potassium  Cyanide,  KCy  =  KCN. — This  compound  is 
prepared  bv  heating  well-dried  potassium  ferrocyanide  to  red- 
ness in  stoneware  retorts.  After  cooling,  the  black  mass  is 
exhausted  with  alcohol;  this  solvent  leaves  a  black  deposit, 
consisting  of  charcoal  and  iron,  and  the  solution  evaporated  in 
vacuo  deposits  the  potassium  cyanide  as  a  white,  crystalline 
mass. 

This  body  crystallizes  in  cubes.  It  has  a  caustic  taste  and 
an  after-taste  of  bitter  almonds.  It  is  very  poisonous.  It  is 
quite  soluble  in  water  and  alcohol.  When  its  aqueous  solution 
is  boiled,  it  disengages  ammonia,  and  is  converted  into  potas- 
sium formate.  This  reaction  takes  place  slowly  in  the  cold, 
and  is  analogous  to  that  which  has  before  been  described. 

When  potassium  cyanide  is  heated  with  sulphur,  it  is  con- 
verted into  potassium  sulphocyanate.  Iodine  dissolves  abun- 
dantly in  a  solution  of  potassium  cyanide ;  potassium  iodide  is 
formed,  and  cyanogen  iodide  is  deposited  in  crystals. 

Solution  of  potassium  cyanide  dissolves  the  insoluble  cya- 
nides of  zinc,  silver,  etc.,  forming  double  cyanides. 

Mercury  Cyanide,  HgCy2  =  Hg(CN)2. — This  compound 
is  prepared  by  dissolving  finely-powdered  mercuric  oxide  in  an 
aqueous  solution  of  hydrocyanic  acid  until  the  odor  of  the  lat- 
ter has  entirely  disappeared,  being  careful  to  avoid  an  excess 
of  the  oxide.  After  concentration  and  cooling,  colorless,  anhy- 
T  37 


434  ELEMENTS    OF    MODERN    CHEMISTRY. 

drous  prisms  are  obtained,  which  are  unaltered  by  air  and  light. 
This  is  mercury  cyanide.  It  is  very  poisonous. 

It  possesses  a  nauseous  metallic  taste,  and  dissolves  in  8 
parts  of  cold  water. 

It  is  decomposed  by  heat  into  mercury  and  cyanogen;  para- 
cyanogen  is  formed  at  the  same  time.  The  solution  of  mer- 
cury cyanide  dissolves  mercuric  oxide,  and  forms  with  it  a 
compound  more  soluble  than  the  cyanide,  crystallizing  in  color- 
less scales. 

If  a  solution  of  potassium  iodide  be  added  to  a  solution  of 
mercuric  cyanide,  a  compound  of  the  two  substances  is  imme- 
diately precipitated  in  beautiful  pearly  scales  (Cailliot). 

FERROCYANIDES. 

By  this  name  are  designated  compounds  containing  cyanogen 
and  iron  intimately  combined  together  and  forming  a  complex 
radical  capable  of  passing  from  one  compound  to  another  by 
double  decomposition.  This  radical,  which  is  called  ferrocy- 
anogen,  contains  one  atom  of  diatomic  iron  combined  with  six 
cyanogen  groups,  CN.  As  each  of  the  latter  represents  one 
atomicity,  it  is  evident  that  the  group  (Cy6-Fe)iv,  in  which 
but  two  atomicities  are  saturated  between  the  Fe  and  2Cy, 
must  be  tetratomic.  Hence  ferrocyanogen  can  combine  with 
four  atoms  of  a  monatomic  metal  such  as  potassium.  The  im- 
portant compound  known  as  potassium  ferrocyanide,  or  yellow 
prussiate  of  potash,  has  such  a  composition. 

Potassium  Ferrocyanide,  K4Cy6Fe  -f  3H20.— This  salt  is 
obtained  by  calcining  animal  matters,  such  as  blood,  horn,  the 
debris  of  skin,  leather,  etc.,  in  closed  iron  vessels  with  potassium 
carbonate.  The  calcined  mass,  which  contains  potassium  cy- 
anide, is  exhausted  with  boiling  water,  and  ferrous  sulphate  is 
added  to  the  solution,  which  is  then  evaporated  to  crystalliza- 
tion ;  or  the  solution  is  boiled  with  metallic  iron,  which  dissolves 
with  evolution  of  hydrogen.  The  iron  may  also  be  added  to 
the  mixture  of  animal  matter  and  potassium  carbonate  before 
calcination  ;  after  cooling,  the  mass  is  pulverized  and  exhausted 
with  boiling  water.  The  solution  contains  ferrocyanide. 

When  sufficiently  concentrated,  it  deposits  the  salt  in  yellow 
crystals,  which  are  derived  from  a  square  octahedron.  They 
are  unaltered  by  the  air,  but  lose  12.8  per  cent,  of  water  at 
100°.  The  anhydrous  salt  is  white. 


POTASSIUM   FERRICYANIDE.  435 

Potassium  ferrocyanide  dissolves  in  2  parts  of  boiling,  and 
in  4  parts  of  cold  water.  It  is  insoluble  in  alcohol.  When 
heated  with  bodies  rich  in  oxygen,  such  as  manganese  dioxide, 
it  is  converted  into  potassium  cyanate,  the  iron  itself  being 
oxidized  to  peroxide.  It  is  not  poisonous. 

When  fused  with  sulphur,  it  is  converted  into  potassium 
sulphocyanate. 

When  heated  with  concentrated  sulphuric  acid,  it  yields  pure 
carbon  monoxide,  and  a  residue  consisting  of  sulphates  of  iron, 
potassium,  and  ammonium. 

Potassium  ferrocyanide  precipitates  many  metallic  solutions. 
The  following  are  some  of  these  precipitates : 
Zinc  ferrocyanide  Zn2Cy6Fe,         white. 

Copper  ferrocyanide         Cu2Cy6Fe,         mahogany  color. 
Lead  ferrocyanide  Pb'2Cy6Fe,         white. 

Silver  ferrocyanide  Ag4Cy6Fe,         white. 

Potassium  ferrocyanide  forms  a  bluish-white  precipitate  with 
ferrous  salts.  This  precipitate  contains : 


It  is  identical  with  the  bluish-white  deposit  which  is  formed  when 
potassium  ferrocyanide  is  heated  with  dilute  sulphuric  acid. 

Prussian  Blue,  (Fe2/(Cy6Fe)3.— This  is  the  dark-blue  pre- 
cipitate obtained  when  a  solution  of  potassium  ferrocyanide  is 
poured  into  a  ferric  salt. 

2Fe2Cl6     +     3K4Cy6Fe     =     12KC1     +     Fe4(Cy6Fe)3 

Ferric  chloride.     Potassium  lerrocj  anide.  Ferric  ferrocyanide. 

(Prussian  blue.) 

The  Prussian  blue  of  commerce  ordinarily  occurs  in  cubical 
fragments,  having  a  fine  blue  color  and  a  coppery  reflection. 

When  calcined  in  contact  with  the  air,  it  leaves  a  residue 
of  peroxide  of  iron.  It  is  insoluble  in  water,  alcohol,  and  in 
the  weaker  acids.  Oxalic  acid  dissolves  it,  and  the  solution  is 
employed  as  a  blue  ink. 

POTASSIUM   FERRICYANIDE. 
(RED  PRUSSIATE  OF  POTASH.) 

K«(Cy6Fe)2 

This  beautiful  salt,  discovered  by  Leopold  Gmelin,  is  formed 
when  a  current  of  chlorine  is  passed  into  a  solution  of  potassium 
ferrocyanide.  Potassium  chloride  and  potassium  ferricyanide 
are  formed,  and  the  latter  gives  to  the  liquid  a  deep  green-brown 


436  ELEMENTS   OF    MODERN   CHEMISTRY. 

color.  On  evaporation  it  deposits  the  new  salt,  which  is  puri- 
fied by  a  second  crystallization.  Potassium  chloride  remains 
in  the  mother-liquor. 

2K*(Cy6Fe)     +     CP     =    2KC1     +     K6(Cy6Fe)2 

Potassium  ferrocyanide.  Potassium  ferricyanide. 

Potassium  ferri cyanide  forms  magnificent  clinorhombic  prisms 
of  a  ruby-red  color.  These  crystals  are  anhydrous.  They  con- 
tain K6Cy12Fe2.  It  is  considered  that  they  contain  a  hexad 
radical,  Cy12Fe2,  formed  by  the  union  of  two  ferrocyanogen 
radicals  (FeCy6-Cy6Fe)vi  =  ferricyanogen. 

Potassium  ferricyanide  dissolves  in  3.8  parts  of  cold  water, 
and  in  a  less  quantity  of  boiling  water.  The  solution  has  a 
dark  yellow-brown  color.  It  does  not  precipitate  the  ferric 
salts.  In  solutions  of  the  ferrous  salts  it  gives  a  blue  precip- 
itate analogous  to  Prussian  blue,  and  which  is  called  TwribuWs 
blue. 
K6(Cy6Fe)2  -f  3FeSO*  =  3K2S04  +  Fe3(Cy6Fe)2 

Potassium  Ferrous  sulphate.  Potassium  Ferrous  ferricyanide. 

.ferricyanide.  sulphate.  (Turnbull's  blue.) 

NITROFERROCYANIDES. 

These  salts,  which  were  discovered  by  Playfair,  are  formed 
by  the  action  of  nitric  acid  upon  certain  alkaline  ferrocyanides. 
The  best  known  is  sodium  nitroferrocyanide,  or,  as  it  is  ordi- 
narily called,  sodium  nitroprusside. 

It  is  prepared  by  oxidizing  potassium  ferrocyanide  with  dilute 
nitric  acid.  After  filtration  and  evaporation,  crystals  of  potas- 
sium nitrate  and  a  deposit  of  oxamide  are  obtained.  The 
mother-liquor  is  saturated  with  sodium  carbonate,  and  on 
evaporation  yields  sodium  nitroprusside,  which  may  be  purified 
by  recrystallization. 

Sodium  nitroferrocyanide  crystallizes  in  large  right  rhombic 
prisms  of  a  ruby-red  color.  Its  composition  is  represented  by 
the  formula  Na2Cy5(NO)Fe  -f  2H2O.  Its  aqueous  solution 
has  a  red-brown  color,  and  gives  a  very  intense  but  evanescent 
purple  color  with  solutions  of  the  alkaline  sulphides. 

CHLORIDES   OF   CYANOGEN. 

There  are  two  chlorides  of  cyanogen  known,  a  chloride, 
CyCl,  which  is  liquid  below  15.5°,  and 'a  solid  chloride,  Cy3CP. 
These  two  chlorides  present  a  curious  instance  of  polymerism. 


CHLORIDES   OF   CYANOGEN.  437 

Liquid  Cyanogen  Chloride,  CyCl  =  CNC1.  —  This  com- 
pound is  prepared  by  passing  chlorine  gas  over  mercury  cy- 
anide, or  better,  into  an  aqueous  solution  of  hydrocyanic  acid, 
which  is  maintained  at  0°.  Hydrochloric  acid  and  cyanogen 
chloride  are  formed. 

HCN  -}-  CP  =  CNC1  +  HC1 

When  the  solution  is  saturated  with  chlorine,  it  is  gently 
heated,  and  the  cyanogen  chloride  which  is  disengaged  is 
passed  through  a  tube  containing  calcium  chloride,  and  con- 
densed in  a  well-cooled  receiver. 

When  properly  purified,  cyanogen  chloride  is  a  colorless 
liquid,  having  a  penetrating  odor,  which  is  very  irritating  to 
the  eyes.  It  boils  at  15.5°  and  solidifies  at  —  5  or  —  6°.  When 
pure,  it  cart  be  preserved  without  alteration,  but  if  it  contain  a 
trace  of  chlorine,  it  soon  becomes  converted  into  the  solid 
chloride. 

Solid  Cyanogen  Chloride,  Cy3CP  =  C3N3C13.—  This  body 
results  from  the  polymeric  transformation  which  the  liquid 
chloride  undergoes  spontaneously  under  certain  circumstances. 
It  can  also  be  obtained  by  exposing  hydrocyanic  acid  to  the 
action  of  chlorine  in  direct  sunlight. 

It  crystallizes  in  brilliant,  yellow  needles  or  plates.  It  melts 
at  140°  and  boils  at  190°.  It  has  a  peculiar,  irritating  odor. 
Boiling  water  immediately  decomposes  it  into  hydrochloric  and 
cyanuric  acids. 


3     +     3HC1 

Cyanogen  chloride.  Cyanuric  acid. 

Cyanogen  Bromide  and  Iodide.  —  The  bromide  and  iodide 
of  cyanogen  correspond  in  constitution  to  the  liquid  chloride. 
They  are  obtained  by  the  action  of  bromine  or  iodine  upon 
mercury  cyanide.  These  elements  decompose  mercury  cyanide 
with  formation  of  bromide  or  iodide  of  mercury,  the  excess 
of  bromine  or  iodine  combining  with  the  cyanogen  to  form 
cyanogen  bromide  or  iodide. 

Cyanogen  bromide,  CNBr,  is  solid  and  crystallizes  in  bril- 
liant cubes.  It  melts  at  4°  and  vaporizes  at  15°. 

Cyanogen  iodide,  CNI,  sublimes  spontaneously  in  beautiful 
colorless  needles  when  a  mixture  of  iodine  and  mercury  cya- 

37* 


438  ELEMENTS   OF   MODERN   CHEMISTRY. 

nide  is  placed  in  the  bottom  of  a  flask.  Mercuric  iodide  is 
formed.  Cyanogen  iodide  has  a  penetrating  odor ;  it  is  very 
volatile  and,  like  the  chloride  and  bromide,  is  very  poisonous. 

COMPOUNDS  OF   CARBON   MONOXIDE. 

Carbon  monoxide  plays  the  part  of  a  diatomic  radical.  It  is 
capable  of  uniting  with  one  atom  of  oxygen  to  form  carbonic  acid 
gas,  or  with  two  atoms  of  chlorine  to  form  chlorocarbonic  gas. 

It  can  also  unite  with  two  residues,  NH2,  which  are  mon- 
atomic  since  they  represent  ammonia  less  one  atom  of  hydro- 
gen ;  lastly,  it  may  unite  with  NH,  which  is  diatomic  since  it 
represents  ammonia  minus  two  atoms  of  hydrogen.  The  com- 
pounds thus  formed  have  the  following  constitutions  : 
CO.O  carbon  dioxide. 

Cl 
C0<^£j      chlorocarbonic  gas. 

C0<™  urea. 
CO(NH)"   cyanic  acid. 

The  last  two  compounds  can  be  considered  as  derived  from 
the  ammonia  type. 

Cyanic  acid  is  derived  from  one  molecule  of  ammonia  by 
the  substitution  of  the  diatomic  radical  CO,  which  is  called 
carbonyl,  for  two  atoms  of  hydrogen. 


(H 

N  \  H 

IH 


f  CO" 
N  j  jj      cyanic  acid. 


Urea  is  derived  from  two  molecules  of  ammonia  by  the  sub- 
stitution of  the  radical  carbonyl  for  two  atoms  of  hydrogen. 

f  H2  ( CO" 

N2  \  H2  N*  \  H2   urea. 

(  H2  (  H2 

Urea  is  then  carbonic  diamide  ;  or  more  simply,  carbamide. 

CYANIC   ACID. 
CONH 

Liebig  and  Wohler  obtained  this  acid  by  the  dry  distillation 
of  cyanuric  acid.  One  molecule  of  the  latter,  which  is  poly- 
meric with  cyanic  acid,  then  breaks  up  into  three  molecules  of 
the  latter  body. 

C3Q3N3H3  =  3CQNH 

Cyanuric  acid.  Cyanic  acid. 


CYANIC   ACID.  439 

The  latter  acid  condenses  at  a  few  degrees  below  0°  to  a  color- 
less liquid  having  a  strong  and  irritating  odor.  It  is  very 
unstable.  As  soon  as  it  is  removed  from  the  freezing  mixture 
in  which  it  is  condensed,  and  its  temperature  rises  to  a  few 
degrees  above  0°,  it  produces  a  crackling  noise  and  little  ex- 
plosions, and  is  converted  by  a  molecular  transformation  into 
an  amorphous  white  mass  called  cyamelide.  The  latter  body 
is  also  formed  at  the  same  time  as  cyanic  acid  by  the  dry  distil- 
lation of  cyanuric  acid. 

Potassium  Cyanate,  KCON. — This  salt  is  prepared  by 
heating  to  dull  redness  in  a  flat  sheet-iron  dish  an  intimate 
mixture  of  2  parts  of  potassium  ferrocyanide  and  1  part  of 
manganese  dioxide,  both  in  fine  powder  and  perfectly  dry. 
The  mixture  must  be  continually  stirred;  it  blackens  and 
enters  into  semi-fusion  ;  after  cooling,  it  is  reduced  to  powder 
and  exhausted  with  hot  alcohol  of  80  per  cent.  On  cooling, 
the  filtered  alcoholic  solution  deposits  potassium  cyanate  in 
laminated,  transparent  crystals  which  are  anhydrous.  This  salt 
is  very  soluble  in  water  and  but  slightly  soluble  in  cold  concen- 
trated alcohol.  If  hydrochloric  acid  be  added  to  an  aqueous  so- 
lution of  potassium  cyanate,  carbonic  acid  gas  is  disengaged  with 
brisk  effervescence.  The  liquid  contains  ammonium  chloride. 
CONH  +  H20  =  CO2  +  NH3 

There  is  a  compound  isomeric  with  potassium  cyanate ;  it  is 
formed  by  the  action  of  cyanogen  chloride  upon  potassium 
hydrate  (Bannow). 

CN.C1     +     2KOH  =  KC1   +    H20     +     KCNO 

Cyanogen  chloride.  Potassium  cyanate. 

The  hydrate  corresponding  to  this  potassium  salt  would  be 
the  true  cyanic  acid,  of  which  the  ethers  were  discovered  by 
Cloez.  The  compound  actually  known  by  the  name  cyanic  acid 
does  not  merit  that  name.  It  is  not  a  compound  of  cyanogen, 
but  a  combination  of  oxide  of  carbon ;  it  is  carbimide.  It  should 
be  called  isocyanic  acid.  The  following  formulae  will  explain 
this  curious  isomerism: 

H-O-ClN  H-N=C=0 

Cyanic  acid.  Isocyanic  acid. 

K-0-C=N  K-N=C=0 

Potassium  cya'iate  (Bannow).         Potassium  isocyanafe  (ordinary  cyanate). 

C2H5-0-CEN  C2H5-N=C=0 

Ethyl  cyanate  Ethyl  isocyanate. 

(Cloez).  (Cyanic  ether  of  Wurtz.) 


440  ELEMENTS    OP    MODERN   CHEMISTRY. 

Ammonium  Cyanate.  —  This  is  formed  when  vapor  of  cyanic 
acid  is  passed  into  a  lla.sk  containing  ammonia  gas.  It  is  a  solid, 
white  mass,  very  soluble  in  water.  When  its  aqueous  solution 
is  treated  with  hydrochloric  acid,  it  disengages  carbon  dioxide 
like  the  solution  of  potassium  cyanate.  If  its  aqueous  solution 
be  boiled,  or  even  left  to  itself  for  several  days,  ammonium 
cyanate  becomes  transformed  into  urea. 


(NH')CON  C0 

Ammonium  cyaoate.  Urea. 

UREA. 

CH*N20 

This  body,  noticed  by  Rouelle  in  1773,  is  the  most  abundant 
of  the  solid  constituents  of  urine,  from  which  it  was  extracted 
by  Fourcroy  and  Vauquelin  in  1799.  Wohler  was  the  first  to 
obtain  urea  artificially  by  combining  cyanic  acid  and  ammonia. 

CONH  +  NH3  =  CH4N20 

This  discovery  was  the  first  instance  of  the  synthesis  of  an 
organic  body. 

Urea  is  also  formed  by  the  action  of  chlorocarbonic  gas  upon 
ammonia  (Natanson). 

CO<C1     +     2NH3      =     CO<NH'     +     2HC1 
Also  by  the  action  of  ammonia  on  ethyl  carbonate. 

+  2NH3  =    CO<NH* 


Ethyl  carbonate.  Urea.  Alcohol. 

These  reactions  show  clearly  that  urea  is  the  amide  corre- 
sponding to  carbonic  acid,  that  is,  carbonic  diamide.  Indeed, 
it  represents  neutral  ammonium  carbonate,  less  two  molecules 
of  water. 

nn<rO.NH4 
<O.NH* 

Preparation.  —  1.  Urea  may  be  obtained  from  urine  by  the 
following  process.  The  urine  is  evaporated  to  a  syrupy  consist. 


UREA.  441 

ence  on  a  water-bath.  It  is  allowed  to  cool,  and  an  excess  of 
cold  nitric  acid  is  added ;  a  mass  of  crystals  are  formed,  which 
ordinarily  have  a  brown  color.  They  are  drained,  washed  with 
a  little  ice-water,  redissolved  in  hot  water,  and  animal  charcoal 
which  has  been  washed  with  hydrochloric  acid  is  added.  The 
whole  is  heated  on  a  water-bath  for  a  few  minutes  and  then 
filtered.  Colorless  crystals  of  urea  nitrate  are  obtained  on 
cooling. 

They  are  suspended  in  water,  and  a  concentrated  solution 
of  potassium  carbonate  is  added  little  by  little,  until  all  effer- 
vescence ceases.  Carbon  dioxide  is  disengaged,  and  potassium 
nitrate  is  formed,  while  the  urea  is  set  free.  The  liquor  is 
evaporated  to  dryness  on  the  water-bath,  and  the  residue  ex- 
hausted with  absolute  alcohol,  which  dissolves  the  urea,  while 
the  potassium  nitrate  remains.  The  alcoholic  solution  is  con- 
centrated, and  urea  crystallizes  out. 

2.  Potassium  cyanate  is  prepared  by  heating  28  parts  of 
well-dried  potassium  ferrocyanide  with  14  parts  of  manganese 
dioxide,  as  has  been  already  indicated.  The  cooled  mass  is 
coarsely  powdered,  and  exhausted  with  cold  water,  which  dis- 
solves the  potassium  cyanate.  20  parts  of  ammonium  sulphate 
are  added  to  the  filtered  liquid,  which  is  then  evaporated  to 
dryness  on  a  water-bath.  The  residue  is  exhausted  with  boil- 
ing alcohol,  which  dissolves  the  urea  and  leaves  potassium  sul- 
phate. 

In  this  operation  the  potassium  cyanate  and  ammonium  sul- 
phate undergo  double  decomposition,  with  formation  of  potas- 
sium sulphate,  and  ammonium  cyanate  which  is  transformed 
into  urea. 

Properties. — Urea  separates  from  its  aqueous  solution  in 
long,  flattened,  and  striated  prisms.  It  sometimes  deposits 
from  its  alcoholic  solution  in  square  prisms. 

The  crystals  are  colorless  and  possess  a  cooling  taste.  They 
dissolve  in  their  own  weight  of  water  at  15°,  and  in  5  parts 
of  cold  alcohol  of  specific  gravity  0.816.  They  are  but  slightly 
soluble  in  ether. 

If  a  solution  of  urea  be  added  to  a  concentrated  solution  of 
chloride  of  lime,  there  is  an  abundant  disengagement  of  gas, 
which  is  a  mixture  of  nitrogen  and  carbon  dioxide.  The  urea 
is  entirely  destroyed. 

CH4N20  +  H20  +  3CP  ==  CO2  +  N2  +  6HC1 
T* 


442  ELEMENTS   OP   MODERN   CHEMISTRY. 

An  aqueous  solution  of  chlorine  produces  the  same  decom- 
position. 

Nitrous  anhydride  instantly  destroys  urea,  with  formation  of 
water,  carbon  dioxide,  and  nitrogen. 

CH4N20  4-  N203  =  CO2  +  2H20  -f  2N2 

When  an  aqueous  solution  of  urea  is  heated  to  140°  in  a 
sealed  tube,  it  absorbs  the  elements  of  water,  and  is  converted 
into  ammonia  and  carbon  dioxide. 

CIPN20  +  H20  =  CO2  +  2NH3 

This  conversion  of  urea  into  carbonate  of  ammonia  takes 
place  spontaneously  in  stale  urine,  under  the  influence  of  a 
peculiar  ferment  (Van  Tieghem). 

Action  of  Heat  on  Urea.  —  Cyanuric  Acid.  —  Urea  fuses 
at  120°.  When  it  is  rapidly  heated  to  a  higher  temperature, 
it  disengages  ammonia  and  leaves  a  white  residue,  which  is 
cyanuric  acid.  This  body  is  tri-cyanic  acid  : 

(CO)=NH 


(CO)=NH 

It  results  from  the  combination  of  three  molecules  of  cyanic 
acid,  which  are  condensed  into  one,  and  held  together  by  the 
nitrogen  which  each  contains.  This  is  indicated  by  the  lines 
of  union  in  the  formula.  Indeed,  the  three  atoms  of  nitrogen 
are  arranged  in  a  sort  of  ring,  so  that  each  of  them  has  an 
atomicity  saturated  by  its  neighbor. 

N 
/\ 

N—  N 

Cyanuric  acid  is  but  slightly  soluble  in  cold  water.  It  sepa- 
rates from  its  boiling  aqueous  solution  in  small,  colorless  crys- 
tals, containing  two  molecules  of  water  of  crystallization. 

By  dry  distillation,  it  is  converted  into  cyanic  acid. 

Compounds  of  Urea  with  Acids.  —  If  nitric  acid  be  added 
to  a  concentrated  solution  of  urea,  the  liquor  assumes  the  form 
of  a  white,  crystalline,  laminated  mass,  composed  of  crystals 
of  urea  nitrate,  CH4N2O.HN03. 


COMPOUND   UREAS.  443 

These  crystals  are  soluble  in  water  and  alcohol.  They 
strongly  redden  litmus  solution.  They  decompose  at  140°, 
disengaging  a  large  quantity  of  gas. 

The  hydrochloride  of  urea,  CH4N2O.HC1,  and  the  oxalate, 
(CH4N20)2C2H204,  are  known.  The  latter  salt  precipitates  in 
small,  colorless,  granular  crystals  when  a  concentrated  solution 
of  oxalic  acid  is  added  to  a  concentrated  solution  of  urea. 

Compounds  of  Urea  with  Oxides  and  with  Salts.— There 
are  several  compounds  of  urea  with  mercuric  oxide.  They 
are  formed  either  by  the  direct  action  of  mercuric  oxide  upon 
urea,  which  dissolves  that  oxide,  or  by  the  reaction  of  mercuric 
chloride  or  nitrate  upon  urea,  which  is  precipitated  by  both  of 
these  salts.  A  solution  of  urea  converts  recently-precipitated 
silver  oxide  into  a  gray  powder,  which  is  a  compound  of  urea 
and  oxide  of  silver.  Among  the  compounds  of  urea  with  the 
various  salts,  that  which  it  forms  with  sodium  chloride  is  the 
most  important.  It  crystallizes  in  colorless,  oblique  rhombic 
prisms,  containing  CH4N2O.NaCl  -f  H20. 

COMPOUND   UREAS. 

The  compounds  which  are  derived  from  urea  by  the  substi- 
tution of  various  alcoholic  radicals  for  hydrogen  are  called 
compound  ureas.  They  are  obtained  either  by  the  action  of 
cyanic  acid  upon  the  compound  ammonias,  or  by  treating  the 
cyanic  ethers  with  ammonia  or  with  the  compound  ammonias 
(Ad.  Wurtz). 

;        CONH     +     N/gP    =    CO<™FH'> 

Cyanic  acid.  Ethylamine.  Ethylurea. 

CON(C2H5)     +     NH3    = 

Ethyl  cyanate.  Ethylurea. 

The  following  is  the  nomenclature  and  composition  of  some 
of  the  principal  compound  ureas : 

CH*N20  urea. 
CH3(CH3)N20  methylurea. 
CH*(C»H5)N*0  ethylurea. 
CH2(C2H5)2N20  diethylurea. 
CH(C2H5)3N20  triethylurea. 
CH3(C5HU)N20  araylurea. 
CH3(C6I15)N20  phenylurea. 
CH2(C6H5)2S*0  diphenylurca. 


444  ELEMENTS   OF   MODERN   CHEMISTRY. 

POTASSIUM   SULPHOCYANATE. 

KCSN 

This  salt,  which  is  sometimes  called  potassium  sulphocyanide, 
corresponds  to  the  cyanate,  in  which  the  oxygen  is  replaced  by 
sulphur. 

It  is  prepared  by  heating  a  mixture  of  two  parts  of  potas- 
sium ferrocyanide  and  one  part  of  sublimed  sulphur  to  redness 
in  a  crucible  or  luted  matrass.  After  cooling,  the  mass  is 
dissolved  in  water,  the  solution  filtered,  and  potassium  carbon- 
ate added  to  the  liquor  as  long  as  a  precipitate  of  ferrous  car- 
bonate is  formed.  The  solution  is  again  filtered,  evaporated  to 
dryness,  the  residue  exhausted  with  alcohol,  and  the  alcoholic 
solution  allowed  to  evaporate  spontaneously. 

Potassium  sulphocyanate  crystallizes  in  long  striated  prisms 
resembling  potassium  nitrate,  or  in  needles  terminated  by  four- 
faced  points.  It  is  deliquescent  and  very  soluble  in  water  and 
alcohol. 

Solution  of  potassium  sulphocyanate  produces  an  intense 
blood-red  color  with  the  ferric  salts,  due  to  the  formation  of 
ferric  sulphocyanate. 

Ammonium  Sulphocyanate,  NH4CSN. — This  body  corre- 
sponds to  ammonium  cyanate.  It  occurs  in  the  water  from  the 
purification  of  coal-gas.  When  heated  to  170° ,  it  is  converted 

NTT2 
into  sulpho-urea,  CS<jJg2,  fusible  at  140°  (Reynolds). 

The  sulphocyanates  present  an  isomerism  exactly  like  that 
which  has  been  mentioned  for  the  cyanates. 


MONATOMIC    ALCOHOLS  AND   THEIR 
DERIVATIVES. 

These  compounds  form  part  of  the  great  class  of  alcohols. 
They  are  neutral  hydrates,  derived  from  hydrocarbons  by  the 
substitution  of  the  radical  hydroxyl  OH  for  an  atom  of  hydro- 
gen. Among  these  bodies,  the  more  important  are  those  which 
belong  to  the  same  series,  as  ordinary  alcohol,  or  ethyl  hydrate, 
which  has  been  indicated  on  page  417.  Wood-spirit,  or  methyl 
hydrate,  is  the  simplest  term  of  the  series.  While  studying  its 
combinations,  in  1835,  Dumas  and  Peligot  were  the  first  to  call 
attention  to  the  function  "  alcohol." 


METHANE.  445 


METHYL   COMPOUNDS. 

In  these  compounds,  we  admit  the  existence  of  a  radical, 
CH3,  to  which  the  name  methyl  is  given.  Wood-spirit  is  its 
hydrate  ;  marsh  gas,  or  methane,  its  hydride.  To  this  hydride 
correspond  a  chloride,  a  bromide,  and  an  iodide.  Chloroform 
is  dichloro-msthylchloride,  or  trichloromathane.  Around  methyl 
hydrate  are  grouped  the  salts  of  methyl  or  methylic  ethers,  re- 
sulting from  the  action  of  the  acids  upon  that  body,  and  which 
are  to  methyl  hydrate  as  the  potassium  salts  are  to  potassium  hy- 
drate. They  are  the  compound  methyl  ethers.  The  following 
formulae  indicate  the  relations  which  exist  between  these  bodies  : 

flTTS 

CH9H  H>0 

Methane,  or  methyl  hydride.  Methyl  hydrate. 

f1TT3 

CH3C1 


Methyl  chloride.  Methyl  oxide. 

CHCP  °2CIP>0 

Chloroform.  Methyl  acetate. 

These  compounds  will  be  but  briefly  described. 

METHANE. 

(MARSH  GAS.) 
CH* 

The  inflammable  gas  which  is  disengaged  from  the  mud  of 
marshes  is  impure  methane.  The  same  gas  is  frequently 
evolved  in  the  galleries  of  coal  mines,  and  constitutes  the 
fire-damp  of  miners.  It  is  produced  artificially  by  the  action 
of  an  excess  of  alkali  upon  acetic  acid  (Persoz,  Dumas). 

Preparation.  —  Methane  is  most  conveniently  prepared  in 
the  pure  state  by  strongly  heating  in  a  glass  flask  or  retort  a 
mixture  of  1  part  of  sodium  acetate,  1  part  of  potassium  hy- 
drate, and  1  £  parts  of  lime  ;  the  lime  is  added  to  prevent  the 
action  of  the  potassium  hydrate  upon  the  glass.  The  gas  may 
be  collected  over  water. 

NaC2H302     +     NaOH     =     CH4     +     Na2C03 

Sodium  acetate.  Methane. 

Properties.  —  Methane  is  a  colorless,  odorless  gas.     Its  den- 

38 


446  ELEMENTS   OF    MODERN    CHEMISTRY. 

sity  is  0.559  ;  it  is  but  slightly  soluble  in  water,  somewhat  more 
so  in  alcohol.  It  burns  in  the  air  with  a  yellow  flame  less  lumi- 
nous than  that  of  ethylene,  or  olefiant  gas.  A  mixture  of  me- 
thane and  oxygen  explodes  violently  on  the  application  of  flame 
or  the  passage  of  an  electric  spark. 

If  two  volumes  of  methane  and  four  volumes  of  oxygen  be 
introduced  into  an  eudiometer  and  the  spark  be  passed,  a  bright 
flash  is  visible.  After  the  combustion,  the  mercury  rises  in  the 
tube,  and  it  is  found  that  the  volume  of  gas  is  reduced  to  one- 
third  of  the  primitive  volume  (to  2  volumes) ;  if  a  solution  of 
potassium  hydrate  be  introduced,  the  whole  of  the  remaining 
gas  will  be  absorbed.  2  volumes  of  methane  produce  in  burning 
2  volumes  of  carbon  dioxide,  and  require  4  volumes  of  oxygen. 
This  experiment  permits  the  determination  of  the  composition 
of  methane. 

2  volumes  of  carbon  dioxide  contain  2  volumes  of  oxygen 
combined  with  1  volume  (1  atom)  of  carbon ;  consequently  two 
volumes  of  marsh  gas  contain  one  atom  of  carbon. 

The  other  two  volumes  of  oxygen  consumed  have  combined 
with  four  volumes  of  hydrogen,  which  are  likewise  contained  in 
two  volumes  of  methane. 

Consequently  two  volumes  of  methane  contain  1  atom  of 
carbon  and  4  atoms  of  hydrogen. 

A  mixture  of  chlorine  and  methane  explodes  when  exposed  to 
direct  sunlight.  In  diffused  daylight,  the  action  is  less  violent, 
especially  if  an  inert  gas,  such  as  carbon  dioxide,  be  added. 
In  this  case,  methyl  chloride  is  formed,  and  in  presence  of  an 
excess  of  chlorine,  chloroform,  and  finally  carbon  tetrachloride. 

CH4  +    GT  =*    HC1  -f  CH3C1  methyl  chloride. 

CH4  +  3C12  =  3HC1  -f  CHCP  chloroform. 

CH4  +  4CP  =  4HC1  -f  CC14      carbon  tetrachloride. 

It  is  seen  that  in  these  reactions  the  chlorine  is  substituted 
for  hydrogen,  atom  for  atom. 

Inversely,  when  chloroform  or  carbon  tetrachloride  is  sub- 
mitted to  the  action  of  nascent  hydrogen,  an  inverse  substitu- 
tion may  be  effected,  and  these  chlorine  compounds  may  be 
converted  into  methane.  This  may  be  accomplished  by  putting 
them  in  contact  with  sodium  amalgam  and  water.  The  latter 
is  decomposed  by  the  sodium,  and  constitutes  a  source  of  hy- 
drogen (Melsens). 

CHOP  +  3H2  =  3HC1  -f  CH* 


METHYL   HYDRATE — METHYL   OXIDE.  44*7 

METHYL  HYDRATE,  OR  METHYL  ALCOHOL. 

(WOOD-SPIRIT.) 
CHK)  =  CH3-OH 

The  products  of  the  dry  distillation  of  wood  contain  about 
one  per  cent,  of  a  spirituous  liquid,  which  was  discovered  in 
1812  by  Taylor,  and  named  wood-spirit.  It  is  separated  by 
several  distillations  and  rectifications  over  lime ;  for,  being  more 
volatile  than  the  other  products,  it  passes  over  first. 

When  pure,  it  is  a  mobile,  colorless  liquid,  having  an  alco- 
holic odor.  It  boils  at  66.5°.  Its  density  at  0°  is  0.8142 
(Dumas  and  PeligotJ. 

It  is  inflammable  and  burns  with  an  almost  colorless  flame. 
It  is  miscible  with  water,  alcohol,  and  ether  in  all  proportions. 
It  dissolves  caustic  baryta  and  forms  with  it  a  definite  combi- 
nation. It  forms  a  crystalline  compound  with  calcium  chloride 
containing  CaCP  -f  4CH40. 

Potassium  and  sodium  react  energetically  upon  methyl  hy- 
drate ;  the  metal  dissolves  with  disengagement  of  hydrogen  and 
formation  of  potassium  or  sodium  methylate. 

CH3-OH  CH3-OK 

Methyl  hydrate.  Potassium  metbylate. 

If  methyl  alcohol  be  placed  under  a  bell-jar  containing  also 
some  watch-glasses  filled  with  platinum  black,  so  that  the  vapor 
of  the  wood-spirit  mixed  with  air  may  come  in  contact  with 
the  finely-divided  metal,  it  is  found  that  the  liquid  aoon  becomes 
strongly  acid.  By  the  slow  oxidation  of  the  wood-spirit  under 
these  conditions,  formic  acid  is  produced  (Dumas  and  Peligot). 

CH3-OH     -f     O2    =     CHO-OH     -f     H20 

Methyl  hydrate.  Formic  acid. 


METHYL  OXIDE. 

(CH8)2O 

When  methyl  alcohol  is  heated  with  twice  its  weight  of 
concentrated  sulphuric  acid,  a  colorless  gas  is  disengaged,  which 
is  methyl  oxide. 

2CH3.OH       =      (CH3)20    +     H20 

Methyl  hydrate.  Methyl  oxide. 


448  ELEMENTS   OF   MODERN   CHEMISTRY. 

This  gas  is  formed  by  the  dehydration  of  methyl  alcohol 
and  the  linking  together  of  two  methyl  groups  by  an  atom  of 
oxygen.  It  is  methylic  ether.  It  holds  the  same  relation  to 
methyl  hydrate  that  ordinary  ether  does  to  ethyl  hydrate. 

It  is  colorless,  very  soluble  in  alcohol  and  ether,  and  quite 
soluble  in  water.  It  liquefies  at  a  very  low  temperature 
(—36°). 

CHLORIDE,  BROMIDE,  AND  IODIDE  OF  METHYL. 

These  compounds  may  be  regarded  as  marsh  gas  in  which 
one  atom  of  hydrogen  is  replaced  by  an  atom  of  chlorine,  bro- 
mine, or  iodine. 

They  are  formed  by  the  action  of  hydrochloric,  hydrobromic, 
and  hydriodic  acids  upon  methyl  alcohol. 

CH'.OH  +  HC1  =  CH3C1  +  H20 

They  may  be  considered  as  derived  from  the  hydracids  by 
the  substitution  of  the  group  methyl  for  the  atom  of  hydrogen, 

HC1  (CH3)C1 

Hydrochloric  acid.  Methyl  chloride. 

Methyl  chloride  is  a  colorless  gas,  having  an  agreeable  odor. 
When  exposed  to  intense  cold,  it  condenses  to  a  liquid  which 
boils  at  — 22°.  When  heated  for  a  considerable  time  with 
a  concentrated  solution  of  potassium  hydrate,  it  is  converted 
into  methyl  alcohol. 

Methyl  bromide,  CH3Br,  is  a  colorless  liquid,  boiling  at 
13°. 

Methyl  iodide,  CH3I,  boils  at  43°  ;  its  density  at  0°  is  2.1992. 
It  is  made  by  gradually  adding  iodine  to  a  mixture  of  methyl 
alcohol  and  amorphous  phosphorus,  and  distilling.  The  dis- 
tilled liquid  is  mixed  with  water,  which  precipitates  the  iodide  ; 
the  dense  liquid  is  separated,  dried  with  calcium  chloride,  and 
distilled. 

CHLOROFORM. 

CHOP 

This  important  substance  was  discovered  in  1831  by  Soubei- 
ran  and  Liebig.  It  is  made  by  distilling  either  alcohol  or  wood- 
spirit  with  a  mixture  of  chloride  of  lime  and  calcium  hydrate. 
The  distilled  liquid  separates  in  two  layers,  of  which  the  lower 


METHYL   CYANIDE.  449 

is  impure  chloroform.  It  is  separated,  washed  first  with  water 
and  then  with  a  solution  of  potassium  carbonate,  and  rectified 
over  calcium  chloride. 

Chloroform  is  a  colorless,  -very  mobile  liquid,  having  an 
agreeable,  ethereal  odor.  Its  density  is  1.48,  and  it  boils  at 
60.8°.  It  does  not  take  fire  on  contact  with  flame. 

It  is  but  slightly  soluble  in  water,  but  dissolves  readily  in 
alcohol  and  ether.  It  dissolves  sulphur,  phosphorus,  fats, 
resins,  a  great  number  of  the  alkaloids,  and  in  general,  organic 
matters  rich  in  carbon. 

By  the  prolonged  action  of  chlorine,  it  is  converted  into 
carbon  tetrachloride,  CC14,  a  colorless  liquid  boiling  at  77°. 

A  boiling  alcoholic  solution  of  potassium  hydrate  converts  it 
into  formate  and  chloride. 

CHOP  +  4KOH  =  2H20  +  3KC1  -f  KCHO2 

Chloroform.  1'otassiuni  formate. 

When  chloroform  is  boiled  with  an  alcoholic  solution  of 
ethylate  of  sodium,  sodium  chloride  is  formed,  together  with 
an  ethereal  compound,  CH(OC2H5)3,  in  which  3  ox  ethyl  groups, 
OC2H5,  replace  the  3  chlorine  atoms  of  chloroform  (Kay). 

CHOP  -f  3NaO.C2H5  =  3NaCl  -f  CH(OC2H5)3 

Chloroform.       Sodium  ethylate.  Kay's  ether. 

Chloroform,  heated  to  180°  with  aqueous  or  alcoholic  ammo- 
nia, yields  ammonium  cyanide  and  sal-ammoniac.     This  re- 
action takes  place  at  100°,  in  presence  of  potassium  hydrate. 
CHC13  +  5NH3  =  NH'CN  +  3NH*C1 

Chloroform  acts  in  a  remarkable  manner  upon  the  phenols 
in  presence  of  an  alkali  such  as  soda  or  potassa,  forming  aro- 
matic aldehydes.  This  reaction,  discovered  by  Reimer,  will  be 
described  farther  on  (see  Phenol). 

Chloroform  is  much  employed  in  surgery  as  an  anaesthetic. 
The  inhalation  of  its  vapor  produces  insensibility  and  loss  of 
muscular  action. 

METHYL   CYANIDE. 
C2H3N  =CH3Cy 

This  body  may  be  obtained  by  distilling  a  mixture  of  potas- 
sium methylsulphate  and  potassium  cyanide,  or  by  distilling 
acetamide  with  phosphoric  anhydride,  which  removes  one  mol- 
ecule of  water  from  the  former  body. 

38* 


450  ELEMENTS   OF    MODERN    CHEMISTRY. 

C2H3O.NH2  —  H20         =         C2H3N 

Acetanride.  Methyl  cyanide,  or 

acetonJtrilp. 

The  product  obtained  in  the  latter  operation  is  called  acc- 
tonitrile. 

Methyl  cyanide  is  a  colorless  liquid,  having  a  disagreeable 
odor  ;  it  boils  at  77°.  A  boiling  solution  of  potassium  hydrate 
decomposes  it  into  ammonia  and  potassium  acetate. 

CH3-CN  -f  2H20  =  CH3-CO.OH  -f  NH3 

Methyl  cyanide.  Acetic  acid. 

Gautier  has  discovered  an  isomeride  of  methyl  cyanide, 
methyl  carbylamine.  This  body  is  formed,  together  with 
methyl  cyanide,  when  a  mixture  of  potassium  methylsulphate 
and  potassium  cyanide  is  distilled.  Under  the  influence  of  alka- 
lies, it  decomposes  into  formic  acid  and  methylamine. 

C£s  }  N  -f  KOH  +  H20    ==    KCHO2  +  C^  j    N 

Methyl  carbylamine.  Potassium  formate.        Methylamine. 

METHYL   NITRATE. 
CH3.NO3 

This  substance,  which  represents  nitric  acid  in  which  the 
basic  hydrogen  is  replaced  by  methyl,  is  an  example  of  a  com- 
pound methyl  ether. 

It  is  prepared  by  introducing  into  a  retort  50  grammes  of 
powdered  potassium  nitrate,  and  adding  a  mixture  of  100 
grammes  of  sulphuric  acid  and  50  grammes  of  wood-spirit. 
The  reaction  begins  in  the  cold,  but  must  be  finished  by  dis- 
tilling on  a  water-bath.  The  liquid  condensed  in  the  receiver 
is  washed  with  water,  and  rectified  several  times  over  a  mix- 
ture of  massicot  and  calcium  chloride. 

It  is  a  colorless,  neutral  liquid  ;  density,  1.182  ;  boiling-point, 
66°.  Its  vapor  explodes  violently  when  heated  above  150°. 

Methyl  nitrate  dissolves  in  ammonia,  producing  ammonium 
nitrate  and  methylamine. 

CH3.N03  -f  2NH3  =  NH4.N03  +  CH3(NH2) 

METHYL   NITRITE   AND   NITROMETHANE. 

These  two  compounds  present  a  remarkable  instance  of 
isomerism  in  very  simple  combinations. 

The  first,  CH3O.NO,  which  represents  nitrous  acid,  HNO2, 


METHYL    NITRITE   AND    NITROMETHANE.  451 

in  which  the  hydrogen  is  replaced  by  methyl,  is  obtained  when 
methyl  alcohol  is  heated  with  nitric  acid  in  presence  of  copper. 
It  is  a  liquid  boiling  at  about  —  12°. 

The  second,  called  also  nitrocarbol,  represents  methane,  in 
which  an  atom  of  hydrogen  is  replaced  by  the  group  (NO2)'. 
CH4  CH3(N02) 

Methane.  Nitromcthane. 

It  is  obtained  by  the  action  of  potassium  nitrite  upon  potas- 
sium monochloracetate  (Kolbe). 

CII2CI.C02K  +  KNO2  -I-  IPO  =  KCl  +  CH3(NO'2)  +  KHCO3 
Potassium  mono-  Potassium  Nitromethane. 

chloracetate.  nitrite. 

It  is  also  produced  by  the  action  of  silver  nitrite  on  methyl 
iodide  (V.  Meyer). 

Nitromethane  is  a  liquid  boiling  between  101  and  102°.  It 
has  an  acid  character,  and  one  of  its  hydrogen  atoms  may  be 
replaced  by  sodium. 

Nitromethane  is  clearly  distinguished  from  methyl  nitrite  by 
the  following  property  :  nascent  hydrogen  transforms  nitrome- 
thane  into  methylamine,  a  reaction  which  does  not  take  place 
with  its  isomeride. 

CH3(N02)     +     3H2    =     CH3.NH2     +     2EPO 

Nitromethane.  Methylamine. 

METHYLNITROLIC  ACID. 


This  remarkable  combination  has  been  obtained  by  V.  Meyer 
by  the  action  of  nitrous  acid  upon  nitromethane. 

CH3(N02)  +  NO.OH     =     CH^N-OH  +  HZ° 

It  is  seen  that  in  this  compound  two  atoms  of  hydrogen  of 
the  methyl  group  CH3,  are  removed  by  an  atom  of  oxygen  of 
the  nitrous  acid,  and  replaced  by  the  residue  (N.OH). 

Methylnitrolic  acid  is  prepared  by  dissolving  5  grammes  of 
nitromethane  in  water,  and  adding  first  a  dilute  solution  of 
potassium  nitrite  cooled  to  0°,  then  dilute  sulphuric  acid  also 
cooled  to  0°,  and  finally  dilute  solution  of  potassium  hydrate 
as  long  as  the  red  color  persists.  At  this  moment,  sulphuric 
acid  is  again  added  until  the  liquid  is  decolorized  ;  the  solution 
is  then  saturated  with  calcium  carbonate,  and  agitated  with 
ether,  which  dissolves  the  methylnitrolic  acid. 


452  ELEMENTS   OF   MODERN   CHEMISTRY. 

After  the  evaporation  of  the  ether,  the  acid  remains  as  large, 
transparent,  colorless  prisms,  fusible  at  54°,  but  decomposing 
at  the  same  time  into  formic  acid  and  nitrogen.  Dilute  sul- 
phuric acid  decomposes  rnethylnitrolic  acid  into  formic  acid  and 
nitrogen  monoxide. 

CH2N203     =     CH202       H-       N20 

Formic  acid.          Nitrogen  monoxide. 

The  crystals  decompose  spontaneously  in  a  few  days. 


FULMINATES   OF   MERCURY  AND  SILVER. 

Among  the  important  compounds  related  to  the  more  simple 
organic  combinations  are  those  explosive  salts  known  ^fulmi- 
nates of  mercury  and  silver. 

They  are  obtained  by  dissolving  mercury  or  silver  in  nitric 
acid  and  adding  alcohol  to  the  still  hot  solution.  In  a  few 
minutes  a  brisk  effervescence  takes  place,  and  fulminate  of 
mercury  or  of  silver  is  deposited  as  a  white,  crystalline  precip- 
itate. When  dry,  these  bodies  explode  violently  by  either  heat 
or  percussion.  Fulminate  of  mercury  is  the  basis  of  percus- 
sion-caps. 

The  composition  of  these  salts  is  interesting;  fulminate  of 
mercury  contains  a  monatomic  group,  (NO2),  a  cyanogen  group, 
(CN),  and  an  atom  of  mercury,  all  three  being  united  to  an 
atom  of  carbon,  of  which  the  four  atomicities  are  thus  perfectly 
satisfied. 

Fulminate  of  silver  has  an  analogous  composition,  but  con- 
tains two  atoms  of  silver. 

The  fulminates  may  thus  be  grouped  with  organic  compounds 
containing  one  atom  of  carbon,  especially  with  the  cyanide  of 
methyl  (Kekule).  The  following  are  some  of  these  com- 
pounds : 

C     H     H     H     H  methane. 

C     H     H     H     Gy  methyl  cyanide. 

C(N02)  H     H     H  nitromethane. 

C(N02)  H     H     Na  sodium-nitromethane. 

C(N02)  H     H     Cl  chloro-nitromethane. 

C(N02)  Cl     Cl    Cl  trichloro-nitromethane  (chloropicrin). 

C(N02)(N02)(N02)H  nitroform. 

C(N02)*  tetranitromethane. 

C(N02)  Ag  Ag  Cy  fulminate  of  silver. 

C(N02)  Hg"       Cy  fulminate  of  mercury. 


CACODYL.  453 

CACODYL,  OR  DIMETHYLARSINE. 


This  interesting  compound  has  long  been  known  in  an  im- 
pure state.  In  1760,  Cadet,  demonstrator  of  chemistry  at  the 
Jardin-du-Roi,  distilled  a  mixture  of  potassium  acetate  and 
white  arsenic  (arsenious  oxide).  He  collected  in  the  receiver 
an  oily  liquid,  having  an  extremely  offensive  odor,  and  pro- 
ducing dense  white  fumes  in  the  air.  Hence  the  name  fuming 
liquor  of  Cadet. 

Bunsen's  investigation  into  the  chemistry  of  this  body  and 
its  combinations  has  become  classic.  According  to  his  re- 
searches, the  fuming  liquor  of  Cadet  is  a  mixture  of  two  bodies, 
one  of  which,  containing  only  carbon,  hydrogen,  and  arsenic, 
plays  the  part  of  a  radical :  it  is  cacodyl ;  the  other  body  is  the 
oxide  of  this  radical. 

To  obtain  cacodyl  in  the  pure  state,  the  crude  product  is 
treated  with  hydrochloric  acid,  which  converts  the  oxide  of 
cacodyl  into  chloride. 

As2(CH3)40     -f     2HC1     =     2As(CH3)2Cl     +    H20 

Dimethylarsine  oxide.  Dimethylarsine  chloride. 

This  chloride,  separated  by  distillation,  and  treated  with  zinc 
at  100°  in  sealed  tubes,  furnishes  free  cacodyl. 

The  latter  is  a  dense  liquid  boiling  at  170°,  and  having  a 
penetrating  arsenical  odor.  It  is  very  poisonous.  It  produces 
dense  white  fumes  in  the  air,  even  taking  fire  spontaneously. 
Its  vapor  density  is  7.101. 

According  to  this  vapor  density,  free  cacodyl  should  be  rep- 
resented by  the  formula  As2(CH3/  =  (CH3/As-As(CH3)2. 

Arsenic  being  either  triatomic  or  pentatomic  it  is  seen  that 
cacodyl  is  not  saturated ;  hence  it  can  directly  fix  chlorine, 
oxygen,  etc.,  yielding  two  series  of  compounds.  Thus,  one 
molecule  of  cacodyl,  As2Me*,  can  fix  1  or  3  molecules  of  chlo- 
rine, forming  the  two  chlorides : 

As2Me*  +  Cl3  ==  2AsMe2Cl 
As2Me*  +  3C12  =  2AsMe2Cl3 

To  the  two  chlorides  correspond  the  bromides,  iodides,  oxides, 
sulphates,  etc.  The  oxides  are 

Cacodyl  oxide     [As(CH3)2]20 
Cacodylic  acid    As(Cli3)2O.OH 


454  ELEMENTS    OP    MODERN    CHEMISTRY. 

Independently  of  the  cacodyl  compounds,  other  combinations 
of  arsenic  and  methyl  are  known,  —  the  methylarsines  and  the 
compounds  of  methylarsonium. 

These  bodies  form  two  series,  which  were  discovered  and 
studied  by  Baeyer,  and  which  belong  to  the  type  AsX3  and 
AsX5.  The  compounds  of  the  first  kind  are  not  saturated,  and 
can  combine  with  Cl2,  or  the  equivalent  of  Cl2,  passing  into  the 
state  of  the  saturated  compounds  of  the  series  AsX5. 

Series  AsX3  Series  AsX& 

As(CH3)3  As(CH8)*Cl 

Triracthylarsinei  Tetramethylarsouium  chloride. 

As(CH3)2Cl  As(CH3)3C12 

Dimethylarsine  monochloride.  Trimetliylarsine  dichloride. 

As(CH3)Cl2  As(CH3)2Cl3 

Monomethylarsine  dichloride.  Dimethylarsine  trichloride. 

AsCl3  As(CH3)Cl* 

Arsenic  trichloride.  Monomethylarsine  tetrachloride. 


It  is  worthy  of  remark  that  the  trichloride  of  arsenic  is 
incapable  of  fixing  Cl2,  and  passing  into  the  state  of  penta- 
chloride. 

These  compounds  need  not  be  described.  It  may  only  be 
mentioned  that  triinethylarsine,  As(CH3)3,  is  formed,  together 
with  cacodyl,  by  the  action  of  methyl  iodide  on  sodium  arsenide. 
It  is  a  liquid  boiling  below  100°. 


ETHYL   COMBINATIONS. 

The  monatomic  residue  (C2H5)'  =  C2H6  —  H,  which  is  the 
radical  of  ordinary  alcohol,  is  called  ethyl.  Numerous  com- 
pounds are  known  into  which  the  radical  enters. 

When  combined  with  hydrogen,  it  forms  a  gas,  C2H6,  which 
is  ethyl  hydride  or  ethane.  The  chloride,  bromide,  iodide,  and 
cyanide  of  ethyl  were  formerly  designated  as  simple  ethers. 

C2H5C1  ethyl  chloride. 

C2H5Br  ethyl  bromide. 

CWl  ethyl  iodide. 

C3H».CN  ethyl  cyanide. 

Ordinary  alcohol  is  the  hydrate,  ether  is  the  oxide  of  ethyl. 

C2HM)H  ethyl  hydrate  (alcohol). 

C2H5-0-C2H5  =  (C2H5)20  ethyl  oxide  (ether). 


ETHYL    HYDRATE.  455 

The  neutral  compound  ethers  are  derived  from  the  corre- 
sponding acids  by  the  substitution  of  the  radical  C2H5  for  their 
basic  hydrogen. 

C2H30-OH  C2H30-OC2H* 

Acetic  acid.  Ethyl  acetate. 

P202  I  OH  P202  I  °'C2H5 

3   1  OH  3   1  O.C2R5 

Oxalic  acid.  Ethyl  oxalate. 

fOH  (O.C'H* 

PO^OH  PO^O.C2H5 

(OH  (o.c2H5 

Phosphoric  acid.  Phosphoric  ether  (triothyl  phosphate). 

Ethyl  exists  in  the  most  diverse  combinations.  It  can  re- 
place the  hydrogen  of  ammonia,  forming  ethylated  bases.  It 
can  unite  with  the  metalloids  and  metals. 

Free  Ethyl,  or  Butane,  C4H10. — When  it  is  sought  to  obtain 
free,  ethyl  by  heating  ethyl  iodide  to  150°  with  zinc  in  sealed 
tubes,  the  radical  combines  with  itself,  its  molecule  being  doubled 
(Frankland). 

2C2H5I  +  Zn  =  Znl2  +  (C2H5/ 

A  gas  is  thus  formed  which  liquefies  at  -f-l°.  It  was 
formerly  named  free  ethyl,  but  is  the  hydride  of  butyl,  or 
butane.  Indeed,  it  is  incapable  of  regenerating  ethyl  compounds 
containing  the  simple  radical  (C2H9).  When  treated  with  bro- 
mine, it  yields  hydrobromic  acid  and  a  bromide  C4H8Br2,  which, 
according  to  Carius,  is  identical  with  butylene  bromide. 

Ethyl  Hydride,  or  Ethane,  C2H6  =  CH3-CH3.— Frank- 
land  obtained  this  gas  by  treating  zinc-ethyl  with  water. 

Zn(C2H5)2     +     2H20     ===     2C2H6     +     Zn(OH)2 

Zinc  ethyl.  Ethane.  Zinc  hydrate. 

It  is  a  colorless  gas,  burning  with  a  slightly  blue,  luminous 
flame.  When  treated  with  chlorine,  it  yields  ethyl  chloride 
and  hydrochloric  acid. 


ETHYL  HYDRATE,  OR  ALCOHOL. 

C2H«O  ==  CH3-CH2.OII 

Alcohol  is  the  product  of  the  fermentation  of  solutions  which 
contain  glucose,  or  a  substance  capable  of  transformation  into 
glucose. 

It  may  be  formed  synthetically  in  various  manners: 

1.  By  passing  ethylene  gas  into  sulphuric  acid  (Hennel  and 


456        ELEMENTS  OP  MODERN  CHEMISTRY. 

Faraday)  and  boiling  the  ethylsulphuric  acid  so  formed  (Ber- 
thelot). 

PITTS  1 

C2H4        +         H2gQ4        =  !g04 

Ethylene.  Ethylsulphuric  acid. 


SO4      +     H20  =     C2H5.OH     +     H2SO* 

Ethylsulphuric  acid.  Alcohol. 

2.  By  heating  ethylene  gas  with  hydriodic  acid  and  decom- 
posing the  ethyl  iodide  so  formed  with  potassium  hydrate  (Ber- 
thelot). 

C2H4    -f  HI      ==  C2H8I 

C2H5I  +  KOH  ==  C2H5.OH  +  KI 

3.  By  bringing  aldehyde  in  contact  with  sodium  amalgam  in 
presence  of  water.     The  nascent  hydrogen  formed  in  this  case 
fixes  upon  the  aldehyde,  converting  it  into  alcohol  (A.  Wurtz). 

C2H<0    -f     H2    =     C2H60 

Aldehyde.  Alcohol. 

Preparation   and   Purification  of  Alcohol—  Alcohol  is 

manufactured  by  distilling  fermented  liquors,  such  as  wine, 
fermented  juice  of  beet>roots,  and  the  product  obtained  from 
the  fermentation  of  malt,  which  is  saccharified  barley,  corn,  or 
other  grain.  The  apparatus  now  used  for  this  operation  has 
reached  such  a  degree  of  perfection  that  alcohol  of  95  per  cent. 
may  be  obtained  immediately  by  one  distillation. 

Absolutely  pure  alcohol  is  obtained  by  rectifying  the  alcohol 
of  commerce  over  substances  avid  of  water,  such  as  anhydrous 
potassium  carbonate,  quick-lime,  or  caustic  baryta.  The  last 
portions  of  water  are  removed,  and  absolute  alcohol  obtained 
by  redistilling  the  rectified  alcohol  with  caustic  baryta.  Or 
some  sodium  may  be  dissolved  in  the  alcohol,  which  may  then 
be  rectified  on  a  water-bath. 

Properties.  —  Alcohol  is  a  colorless,  mobile  liquid,  having  an 
agreeable,  spirituous  odor.  Density  at  0°,  0.8095.  Boiling- 
point,  78.4°  at  the  normal  pressure. 

Alcohol  mixes  with  water  and  ether  in  all  proportions.  Its 
mixture  with  water  takes  place  with  elevation  of  temperature 
and  contraction  of  volume.  The  maximum  contraction  takes 
place  when  the  two  bodies  are  mixed  in  the  proportion  of  one 
molecule  of  alcohol  (53.94  parts)  to  three  molecules  of  water 
(49.84  parts). 


ETHYL   HYDRATE.  457 

Alcohol  absorbs  moisture  when  exposed  to  the  air.  It  dis- 
solves many  gases,  liquids,  and  solids.  Tinctures  are  solutions 
of  various  medicinal  substances  in  alcohol. 

Among  the  simple  bodies  which  are  soluble  in  alcohol  may 
be  mentioned  iodine.  Potassium  and  sodium  hydrates  dissolve 
in  it  readily,  and  it  is  the  same  with  most  of  the  mineral  acids. 
Many  of  the  chlorides  are  soluble  in  alcohol ;  such  are  those  of 
calcium,  strontium,  zinc,  and  cadmium,  ferric,  cupric,  mercuric, 
and  auric  chlorides. 

Alcohol  dissolves  the  natural  alkaloids,  the  essential  oils, 
resins,  and  fatty  bodies,  the  latter,  however,  less  readily  than 
ether. 

Decompositions. — When  vapor  of  alcohol  is  passed  through 
a  red-hot  porcelain  tube,  it  is  decomposed  into  water,  carbon 
monoxide,  hydrogen,  methane,  and  ethylene.  Besides  this, 
carbon  is  deposited  in  the  porcelain  tube,  and  a  small  quantity 
of  naphthaline  is  produced  (Th.  de  Saussure),  as  well  as 
benzol  and  phenol  (Berthelot).  The  principal  products  of 
the  decomposition  of  alcohol  at  a  dull-red  heat  are  methane, 
hydrogen,  and  carbon  monoxide. 

C2H60  =  CO  +  CH4  -f  H2 

On  the  application  of  a  burning  body,  alcohol  takes  fire 
and  burns  with  a  slightly  luminous,  bluish  flame.  On  contact 
with  platinum  black,  alcohol  vapor  mixed  with  air  undergoes  a 
slow  combustion,  which  produces  successively  aldehyde  and 
acetic  acid. 

C2H60  +  O  =  C2H*O  +  H20 

Alcohol.  Aldehyde. 

C2H40  +  0  =  C2H402 

Aldehyde.  Acetic  Acid. 

Acetic  ether  and  a  small  quantity  of  a  volatile,  neutral  body, 
called  acetal,  are  at  the  same  time  formed  as  accessory  products 
(Stas). 

The  lamp  without  flame  of  Dobereiner  depends  upon  the 
slow  combustion  of  alcohol.  The  wick  of  an  ordinary  spirit- 
lamp  is  surmounted  by  a  spiral  of  platinum  wire,  so  that  when 
the  lamp  is  lighted  the  spiral  is  heated  to  incandescence.  If 
then  the  flame  be  extinguished,  by  covering  it  for  an  instant 
with  a  test-tube,  the  alcohol  vapor  continues  to  rise  with  the 
air  around  the  still  hot  spiral,  and  undergoes  a  slow  combustion. 
But  the  latter  develops  heat,  and  the  spiral  rapidly  becomes 
u  39 


458  ELEMENTS   OF   MODERN   CHEMISTRY. 

heated  to  incandescence,  and  if  the  current  of  air  be  regulated 
by  a  small  glass  chimney,  the  experiment  may  continue  as  long 
as  the  wick  emits  vapor  of  alcohol  in  sufficient  quantity. 

Bodies  rich  in  oxygen  oxidize  alcohol  at  ordinary  tempera- 
tures ;  such  are  chloric  and  chromic  acids.  If  a  little  alcohol 
be  poured  upon  some  chromic  acid  placed  upon  a  brick,  the 
liquid  is  immediately  inflamed  and  the  chromic  acid  reduced 
to  chromium  oxide. 

Chlorine  attacks  alcohol  with  great  energy,  the  final  product 
of  the  reaction  being  a  body  which  has  received  the  name 
chloral  (Liebig,  Dumas). 

If  a  small  piece  of  potassium  or  sodium  be  thrown  into  pure 
alcohol,  the  metal  soon  melts,  and  then  dissolves  with  disen- 
gagement of  hydrogen.  The  product  of  the  reaction  is  a  crys- 
talline, solid  matter  which  is  ethylate  of  potassium  or  sodium, 
that  is,  a  body  derived  from  alcohol  by  the  substitution  of  an 
atom  of  an  alkaline  metal  for  an  atom  of  hydrogen. 


K  Na 

Alcohol.  Potassium  ethylate.          Sodium  ethylate. 

Uses  of  Alcohol,  —  Alcohol  is  used  as  a  combustible  in  spirit- 
lamps.  In  the  arts,  it  is  employed  in  the  manufacture  of  ether, 
chloroform,  eau  de  cologne,  and  many  other  products.  It  is 
largely  used  in  the  laboratory,  and  in  pharmacy,  as  a  solvent  ; 
it  serves  for  the  preservation  of  anatomical  specimens.  In 
France  and  England,  alcohol  employed  for  certain  industrial 
uses  is  exempted  from  part  of  the  tax,  when  it  has  previously 
been  mixed  with  about  one-tenth  of  wood-spirit  and  a  few 
per  cent,  of  mineral  oils  and  resin.  Such  a  mixture  is  unfit 
for  the  manufacture  of  brandy  and  liquors,  but  its  usefulness 
as  a  solvent  is  in  many  cases  unimpaired. 

Alcohol  exists  in  fermented  liquors,  such  as  wine,  cider,  and 
beer.  It  is  contained  in  much  larger  quantities  in  brandies, 
whiskeys,  and  spirits.  These  are  products  of  the  distillation  of 
various  alcoholic  liquids.  They  are  more  or  less  rich  in  alco- 
hol. Brandy  is  prepared  by  the  distillation  of  wine,  cider,  or 
the  products  of  fermentation  of  cherry-juice  (cherry-brandy), 
sugar-cane  (rum),  beet-root  molasses  (beet-brandy).  Whiskey 
is  distilled  from  fermented  starchy  materials,  such  as  corn,  rye, 
potatoes,  etc.,  the  starch  being  first  saccharified.  The  richness 
of  these  materials  in  alcohol  is  indicated  by  the  degrees  of  an 


ETHYL   OXIDE.  459 

alcoholometer.     The  following  table  gives  the  strength  of  some 
of  these  liquors. 

PERCENTAGE  OF 

CAR-TIER'S  AREOMETER.  ALCOHOL. 

BY  VOLUME. 
Weak  brandy     .........     16°  37.9 

Proof  spirits        .........     19°  50.1 

Strong  brandy    .     .     .     .     .....     22°  59.2 

Ordinary  alcohol     ........     33°  85.1 

Rectified  alcohol  (strongest  commercial)    40°  95. 

Absolute  alcohol      ........     41.2°  100. 

ETHYL  OXIDE,  OR  ETHER. 


If  ethyl  iodide  be  added  to  an  alcoholic  solution  of  ethylate 
of  sodium  and  a  gentle  heat  be  applied,  a  deposit  of  sodium 
iodide  is  formed  and  vapors  are  disengaged  which  may  be  con- 
densed in  a  cooled  receiver  into  an  ethereal  liquid.  It  is 
oxide  of  ethyl. 


C'H'I         + 

Etliyl  iodide.  Sodium  ethylate.  Ethyl  oxide. 

If,  in  the  preceding  experiment,  the  ethyl  iodide  be  replaced 
by  methyl  iodide,  an  extremely  volatile  liquid  will  be  formed, 
which  is  the  double  oxide  of  methyl  and  ethyl. 


CH3I    +  0    _    Nal    + 

Methyl  iodide.  Oxide  of  methyl  and  ethyl. 

These  classic  experiments,  due  to  Williamson,  show  that 
the  oxide  of  ethyl  contains  two  ethyl  groups.  It  may  be 
regarded  as  alcohol  in  which  the  hydrogen  atom  of  the  group 
hydroxyl  is  replaced  by  ethyl. 

H-O-H  C2H5-0-H  C2H5-0-C2H5 

Water.  Alcohol.  Ethyl  oxide. 

Preparation.  —  Ether  is  prepared  in  the  arts  by  the  action 
of  sulphuric  acid  on  alcohol.  A  mixture  of  9  parts  of  con- 
centrated sulphuric  acid  and  5  parts  of  alcohol  of  90  per  cent. 
is  heated  in  a  flask,  A  (Fig.  122),  and  a  small,  continuous 
stream  of  alcohol  is  allowed  to  flow  into  this  mixture  through 
the  funnel-tube  a.  The  temperature  of  the  liquid,  indicated  by 
the  thermometer  £,  should  not  exceed  140  or  145°.  The  vapOr 
disengaged  is  condensed  in  a  Liebig's  condenser,  B,  through 
which  a  stream  of  cold  water  flows  continually.  Under  these 


460 


ELEMENTS    OF    MODERN    CHEMISTRY. 


conditions,  a  mixture  of  ether  and  water  collects  in  the  re- 
ceiver D,  together  with  a  little  alcohol,  and  towards  the  close 
of  the  operation,  a  small  quantity  of  sulphurous  acid  gas  is 
disengaged.  The  product  is  purified  by  washing  with  milk  of 
lime,  and  then  with  pure  water,  after  which  it  is  rectified  over 
calcium  chloride  on  a  water-bath.  Fig.  122  represents  the 
apparatus  used  for  public  demonstration ;  in  the  arts,  the  opera- 
tion is  conducted  on  a  large  scale  in  apparatus  of  an  analogous 
construction. 


FIG.  122. 

Theory  of  Etherification.  —The  transformation  of  alcohol 
into  ether  is  a  true  dehydration,  brought  about  by  the  sul- 
phuric acid. 

2(C2H5.OH)  =  (C2H5)20  +  H20 

Williamson  clearly  proved  that  it  is  effected  in  two  distinct 
phases ;  in  the  first,  ethylsulphuric  acid  and  water  are  formed. 


C!HH>° 

Alcohol. 


H20 


Sulphuric  acid. 


Ethylsulphuric  acid. 


ETHYL   OXIDE.  461 

In  the  second,  another  molecule  of  alcohol  reacts  with  the 
ethylsulphuric  acid;  ether  is  formed  and  sulphuric  acid  is 
regenerated. 


Ethylsulphuric  acid.         Alcohol.  Ether.          Sulphuric  acid. 

Hence  the  ether  and  water  collected  in  the  receiver  are  pro- 
ducts of  two  distinct  phases  of  the  reaction.  Ethylsulphuric 
acid  is  continually  formed  and  as  continually  decomposed, 
regenerating  sulphuric  acid  ready  to  act  upon  new  por- 
tions of  alcohol.  However,  although  the  operation  is  con- 
tinuous, it  cannot  go  on  indefinitely,  for  the  mixture  blackens 
after  a  time  and  becomes  unfit  to  etherify  new  quantities  of 
alcohol. 

Properties  of  Ether.  —  Ether  is  a  colorless,  very  mobile 
liquid  ;  its  taste  is  at  first  burning,  then  cooling  ;  its  odor  is  suave 
and  agreeable,  and  is  called  ethereal.  Density  at  0°,  0.7366. 
Boiling-point  under  the  normal  pressure,  34.5°. 

It  is  but  slightly  miscible  with  water,  on  the  surface  of  which 
it  forms  a  separate  layer.  9  parts  of  water  dissolve  1  part  of 
ether  ;  36  parts  of  ether  dissolve  1  part  of  water.  Ether  dis- 
solves in  all  proportions  in  alcohol  and  in  methyl  alcohol. 

It  slightly  dissolves  sulphur  and  phosphorus,  and  notable 
quantities  of  bromine,  iodine,  ferric,  mercuric,  and  auric  chlo- 
rides, and  many  organic  bodies,  such  as  the  oils,  fats,  resins, 
alkaloids,  etc. 

It  is  very  inflammable  and  burns  with  a  quite  luminous 
flame.  Its  vapor  explodes  violently  when  mixed  with  air  or 
oxygen  and  ignited. 

If  a  heated  spiral  of  platinum  wire  be  suspended  in  a  glass 
jar  containing  a  little  ether,  in  such  a  manner  that  the  lower 
extremity  of  the  wire  is  but  a  little  distance  from  the  surface 
of  the  liquid,  the  wire  will  soon  become  brightly  incandescent 
and  will  ignite  the  ether. 

This  effect  is  due  to  the  ether  vapor,  which,  coming  in  con- 
tact with  the  platinum,  and  being  mixed  with  air,  undergoes  a 
slow  combustion.  Heat  is  thus  developed,  and  the  wire  be- 
comes incandescent. 

Chlorine  acts  on  ether  with  extreme  energy.  If  the  action 
be  moderated,  various  products  of  substitution  are  obtained, 
among  which  the  following  have  been  well  studied  : 

39* 


462  ELEMENTS   OF   MODERN   CHEMISTRY. 


Monochlorether  (2H5>0  liquid  boilinS  at  98-99°. 

Dichlorether  C2^32H5>0  li(luid  boiling  at  140-147°. 

r^2H3p]2 

Tetrachlorether  l^0  li(luid»  density  1.5. 


Perchlorether  25^>^      colorless  crystals,  fusible  at  69°. 


The  last  is  a  solid  body,  crystallizing  in  octahedra.  By  the 
action  of  heat  it  is  decomposed  into  carbon  sesquichloride  and 
perchloraldehyde  (Malaguti). 


+        C*C1*0 

Perchlorether.  Carbou  sesquichloride.        Perchloraldehyde. 

When  two  parts  of  bromine  are  added  to  one  part  of  ether, 
and  the  mixture  is  cooled,  a  garnet-colored  liquid  separates 
and  soon  crystallizes.  It  is  a  compound  of  bromine  and  ether, 
(C2H5)2O.Br2,  which  crystallizes  in  thin,  red  plates,  fusible  at 
22°  ;  it  is  easily  decomposed  (Schiitzenberger). 


SULPHYDRATE  AND  SULPHIDE  OF  ETHYL. 

Two  bodies  are  known  which  are  intimately  related,  as  re- 
gards their  constitutions,  with  alcohol  and  ether.  They  are 
the  sulphydrate  and  the  sulphide  of  ethyl.  The  first,  formerly 
known  as  mercaptan,  represents  alcohol  containing  an  atom  of 
sulphur  instead  of  an  atom  of  oxygen ;  the  second  represents 
ether  in  which  the  oxygen  atom  is  replaced  by  sulphur. 

C2H5.OH  (C2H5)2O 

Ethyl  hydrate.  Ethyl  oxide. 

C2H5.SH  (C2H5)2S 

Ethyl  sulphydrate.  Ethyl  sulphide. 

Ethyl  sulphydrate  is  obtained  by  distilling  a  concentrated 
aqueous  solution  of  potassium  sulphydrate  with  a  solution  of 
potassium  ethylsulphate. 

It  may  also  be  prepared  by  passing  vapor  of  ethyl  chloride 
into  an  alcoholic  solution  of  potassium  sulphydrate.  The  liquid 
is  distilled  as  soon  as  it  is  saturated  with  ethyl  chloride,  and 
water  is  added  to  the  distillate.  Ethyl  sulphydrate  separates. 

KSH  +     C2H5C1     =    KC1    +     CTP.SH 

Potassium  sulphydrate.         Ethyl  chloride.  Ethyl  sulphydrate. 


ETHYL   CHLORIDE.  463 

Ethyl  sulphydrate  is  a  transparent,  colorless  liquid,  very  mo- 
bile, and  having  a  fetid  odor.  Density  at  21°,  0.835.  Boil- 
ing-point, 36.2°  (Liebig). 

It  reacts  energetically  with  mercuric  oxide,  forming  water 
and  a  white,  crystalline  body  which  represents  ethyl  sulphy- 
drate in  which  the  hydrogen  is  replaced  by  mercury.  Hence 
the  name  mercaptan  (mercurium  captans),  given  to  the  sulphy- 
drate of  ethyl  by  Zeise.  This  mercuric  compound  is  insoluble 
in  water;  it  contains  (C2IPS)2Hg". 

Ethyl  sulphide  is  obtained,  like  the  sulphydrate,  by  double 
decomposition.  Vapor  of  ethyl  chloride  is  passed  into  an  alco- 
holic solution  of  potassium  monosulphide. 

K2S        +       2C2H5C1      =     2KC1     +     (C2H5)2S 

Potassium  sulphide.  Ethyl  chloride.  Ethyl  sulphide. 

Ethyl  sulphide  is  a  colorless  liquid,  having  a  garlicky  odor. 
It  boils  at  75°.  It  is  insoluble  in  water. 


ETHYL   CHLORIDE. 
C2H5C1 

This  body  is  prepared  by  saturating  alcohol  with  hydrochloric 
acid  gas  and  distilling  on  a  water-bath.  Ethyl  chloride  is  dis- 
engaged, and  should  be  passed  first  through  a  wash-bottle  and 
then  through  a  tube  containing  calcium  chloride,  after  which  it 
may  be  condensed  in  a  receiver  placed  in  a  freezing  mixture. 

Below  11°  ethyl  chloride  is  a  mobile,  colorless  liquid,  having 
a  penetrating  and  agreeable  odor.  It  boils  at  11°  ;  it  is  inflam- 
mable, and  burns  with  a  flame  tinged  with  green. 

If  some  solution  of  silver  nitrate  be  agitated  in  a  jar  con- 
taining vapor  of  ethyl  chloride,  no  precipitate  will  be  formed ; 
but  if  the  agitation  be  continued  after  the  vapor  has  been 
ignited,  an  abundant  precipitate  of  silver  chloride  will  be 
formed,  owing  to  decomposition  of  the  silver  nitrate  by  the  hy- 
drochloric acid  produced  by  combustion  of  the  ethyl  chloride. 

Ethyl  chloride  produces  a  precipitate  of  silver  chloride  when 
passed  into  an  alcoholic  solution  of  silver  nitrate. 

Chlorinated  Derivatives  of  Ethyl  Chloride. — When  ethyl 
chloride  is  submitted  to  the  action  of  chlorine,  various  com- 
pounds are  successively  formed  by  the  substitution  of  chlorine 
for  hydrogen,  atom  for  atom.  The  following  is  the  nomencla- 


464  ELEMENTS    OF    MODERN    CHEMIETRY. 

ture  and  composition  of  these  chlorinated  compounds,  which 
were  discovered  by  V.  Regnault. 

C2H5CI    ethyl  chloride. 

C2H*C12  dichlorethane  (ethylidine  chloride)—  boils  at  57.5°. 

C2H3CI3  trichlorethane—  boils  at  75°. 

C2H2C1*  tetrachlorethane—  boils  at  127.5°. 

C2HC15  pentachlorethane—  boils  at  158°. 

C2C16       hexachlorethane  (sesquichloride  of  carbon). 

It  will  be  noticed  that  the  second  of  these  compounds  is 
isomeric  with  ethylene  chloride,  or  Dutch  liquid,  of  which  the 
description  will  be  found  farther  on.  It  may  be  obtained  by 
treating  aldehyde  with  phosphorus  pentachloride. 

CH3-CHO     +  PCI5  =  CH3-CHC12     -f     POOP 

Aldehyde.  Dichlorethane.      Phosphorus  oxychloride. 

This  mode  of  formation  indicates  its  constitution,  which  is 
expressed  by  the  formula 

CH3 
CHOP 

To  distinguish  it  from  its  isomeride  ethylene  chloride, 
CH2C1 

CH2C1 
it  is  named  dichlorethane  or  ethylidene  chloride. 

In  the  sesquichloride  of  carbon,  C2C16,  the  hydrogen  atoms 
are  all  replaced  by  chlorine.  Carbon  sesquichloride  is  a  crys- 
stalline  solid,  melting  at  162°,  and  boiling  at  182°  (Faraday). 

ETHYL  IODIDE. 


This  important  compound  is  prepared  by  the  action  of  alco- 
hol on  iodine  in  presence  of  amorphous  phosphorus.  Phos- 
phorus iodide  is  formed,  and  reacts  upon  the  alcohol,  yielding 
ethyl  iodide  and  an  acid  of  phosphorus.  The  former  distils 
into  the  receiver,  together  with  the  alcohol  which  escapes  the 
reaction.  Water  is  added,  and  the  lower  layer  of  liquid  is 
separated,  dried  with  calcium  chloride,  and  rectified  on  a  water- 
bath. 

Ethyl  iodide  is  a  colorless  liquid,  but  becomes  brown  when 
long  kept,  especially  when  exposed  to  light.  Density  at  0°, 
1.9753.  Boiling-point,  72.2°. 


ETHYL    CYANIDE.  465 

It  can  exchange  its  iodine  by  double  decomposition,  as  can 
potassium  iodide.  If  ethyl  iodide  be  added  to  an  alcoholic 
solution  of  silver  nitrate,  a  yellow  precipitate  of  silver  iodide 
is  at  once  formed,  while  ethyl  nitrate  remains  in  solution. 

C2H5I     -|-     AgNO3     =     Agl     +     (C2H5)NO3 

Ethyl  iodide.  Silver  nitrate.  Ethyl  nitrate. 

ETHYL   CYANIDE. 


This  compound  is  formed  when  ammonium  propionate  is 
distilled  with  phosphoric  anhydride. 

(NH4)C*H8O1    =    OTPN     +     2H20 

Ammonium  propionate.        Ethyl  cyanide. 

From  this  mode  of  formation,  ethyl  cyanide  is  sometimes 
called  propionitrile.  The  same  body  exists  in  the  product  of 
the  distillation  of  a  mixture  of  potassium  cyanide  and  potassium 
ethylsulphate. 

KCN  +      C2I^>SO*     =     £>SO*      +      C2H5-CN 

Potassium  Potassium  Potassium  Ethyl  cyanide. 

cyanide.        ethylsulphate.  sulphate. 

But  this  product,  which  is  liquid  and  has  a  variable  boiling- 
point,  contains,  independently  of  the  true  cyanide  of  ethyl,  an 
isomeride  of  that  body,  whose  existence  was  foreseen  by  Meyer 
and  discovered  by  Gautier  in  the  product  of  the  action  of 
ethyl  iodide  on  silver  cyanide. 

Ethyl  cyanide  is  a  colorless  liquid  having  a  penetrating  and 
pleasant  odor.  It  boils  at  96.*7° 

When  it  is  boiled  with  potassium  hydrate,  potassium  propio- 
nate is  formed  and  ammonia  is  disengaged  (Dumas,  Malaguti, 
and  Le  Blanc). 

C3H5N    -|-    KOH    +    H20    =    KC3H5O2    +    NHS 

Ethyl  cyanide.  Potassium  propionate. 

When  ethyl  cyanide  is  brought  into  contact  with  dilute  sul- 
phuric acid  and  zinc,  it  fixes  4  atoms  of  hydrogen  and  is 
converted  into  propylamine  (Mendius). 

C4PN     +     H*     =     C3H9N 

Ethyl  cyanide.  Propylamine. 

Ethylcarbylamine.  —  This  name  was  given  by  Gautier  to  the 
isomeride  of  ethyl  cyanide  already  mentioned.  It  is  a  color- 
less liquid,  having  a  very  penetrating  and  intensely  offensive 

u* 


466  ELEMENTS   OF   MODERN   CHEMISTRY. 

odor.     It  boils  at  79°.     With  potassium  hydrate  it  yields  po- 
tassium formate  and  ethylamine. 


*    +    KOH  +  H20  =     H  — N    -I-    ECHO2 

H/ 

Ethylcarbylamiae.  Ethylamine.          Potassium 

formate. 

ETHYL  NITRITE,  OR  NITROUS  ETHER. 
C2H5.O-NO 

This  compound  is  obtained  by  the  action  of  nitric  acid  on 
alcohol.  The  reaction  is  very  violent,  and  abundant  red  vapors 
are  evolved.  After  passing  through  a  wash-bottle,  they  are 
conducted  into  a  well- cooled  receiver,  where  the  ethyl  nitrite 
condenses. 

It  is  a  yellowish,  very  volatile  liquid,  whose  odor  recalls  that 
of  apples.  It  boils  at  18°.  It  is  but  slightly  soluble  in 
water.  Hot  water  immediately  decomposes  it  into  alcohol  and 
nitrous  acid,  the  latter  being  itself  decomposed  into  nitric  acid 
and  nitrogen  dioxide. 

NITRETHANE  AND  ITS  DERIVATIVES. 
C2H*-NO2 

This  isomeride  of  ethyl  nitrite  represents  ethane,  C2H6,  in 
which  one  atom  of  hydrogen  is  replaced  by  the  group  (NO2)'. 
It  is  the  superior  homologue  of  nitromethane. 

It  is  obtained,  together  with  a  certain  quantity  of  ethyl 
nitrite,  when  ethyl  iodide  is  treated  with  silver  nitrite. 

C2H5I     -f     AgNO2    =     C2H5(N02)     +     Agl 

Ethyl  iodide.  Silver  nitrite.  Nitrethane. 

It  is  a  liquid  having  a  peculiar,  ethereal  odor  and  boiling  at 
113-114°.  Density  at  13°,  1.0582  (V.  Meyer). 

With  nascent  hydrogen,  it  furnishes  pure  ethylamine. 
C2H3(N02)  +  3H2  =;  C2H5(NH2)  +  2H20 

All  of  the  homologues  of  nitrethane  thus  yield  the  corre- 
sponding amines.  It  is  a  general  character  of  the  nitro  com- 
pounds, and  one  which  is  not  possessed  by  their  isomerides, 
the  nitrous  ethers.  In  constitution  and  properties,  nitrethane 


ETHYL   NITRATE.  46*7 

approaches  nitrobenzol,  as  will  be  seen  by  the  following  com- 
parison of  their  formulae: 

C2H5.H  C6H5.H 

Ethane.  Benzol. 

C2H5(N02)  C6H5(N02) 

Nitrethane.  Nitrobenzol. 

C2H5(NH2)  C6H5(NH2) 

Ethylamine.  Phenylamine  (aniline). 

The  presence  of  the  group  (NO2)  confers  acid  properties 

NO2 
upon  nitrethane.     Its  sodium  compound,  C2!!4^^     ,  is  formed 

either  by  the  action  of  an  alcoholic  solution  of  sodium  hydrate 
on  nitrethane,  or  by  the  direct  action  of  sodium  on  the  same 
body;  in  the  latter  case  hydrogen  is  disengaged.  Sodium- 
nitrethane  is  very  explosive  (V.  Meyer  and  Stuber). 

When  it  is  sought  to  prepare  potassium-nitrethane  by  the 
action  of  alcoholic  potassium  hydrate  on  nitrethane,  the  latter 
body  is  decomposed,  yielding,  among  other  products,  potassium 
nitrite.  Now,  the  latter  salt  exerts  a  remarkable  action  on  ni- 
trethane, giving  rise  to  a  new  body  of  complex  composition, 
potassium  ethylnitrolate. 

Ethylnitrolic  acid  may  be  obtained  by  a  process  analogous  to 
that  which  has  been  described  for  the  preparation  of  methyl- 
nitrolic  acid.     Ethylnitrolic  acid  contains 
CH3 

C-N.OH 

NO2 

It  crystallizes  in  light-yellow,  transparent  prisms,  possessing 
a  feeble  bluish  fluorescence  and  a  very  sweet  taste.  It  decom- 
poses without  violence  at  81-82°  into  nitrogen,  nitrous  vapors, 
and  acetic  acid.  When  boiled  with  dilute  sulphuric  acid,  it 
decomposes  into  acetic  acid  and  nitrogen  monoxide. 
C2H4N203  =  C2H402  +  N20 

Ethylnitrolic  acid.  Acetic  acid. 

ETHYL  NITRATE,  OR  NITRIC  ETHER. 

(C2H5)NO3 

This  is  obtained  by  the  action  of  nitric  acid  upon  alcohol  in 
presence  of  a  small  quantity  of  urea.  The  latter  body  prevents 
the  reduction  of  the  nitric  acid  to  nitrous  acid.  Nitric  ether 


468  ELEMENTS    OF    MODERN    CHEMISTRY. 

condenses  in  the  receiver.  It  is  washed  with  water,  dehydrated 
with  calcium  chloride,  and  rectified.  It  is  a  liquid,  having  an 
agreeable,  ethereal  odor.  It  boils  at  86°.  Density  at  0°,  1.1322. 
Potassium  hydrate  decomposes  it,  like  all  compound  ethers, 
forming  potassium  nitrate  and  alcohol. 

(C2H5)N03  +  KOH  —  C2H5.OH  +  KNO3 

It  dissolves  in  ammonia,  especially  if  the  latter  be  warm, 
yielding  ammonium  nitrate  and  ethylamine.  The  reaction  is 
analogous  to  that  of  ammonia  upon  methyl  nitrate. 

ETHYL    CYANATE. 

C2H5-N=CO 

This  compound  is  prepared  by  distilling  on  an  oil-bath  a 
mixture  of  2  parts  of  potassium  ethylsulphate  and  1  part  of 
recently-prepared  and  well-dried  potassium  cyanate.  The  pro- 
duct which  condenses  in  the  receiver  is  rectified  on  a  water- 
bath  (Wurtz).  Ethyl  cyanate  is  a  colorless  liquid,  having  a 
very  irritating  odor.  It  boils  at  60°.  Potassium  hydrate  de- 
composes it  into  carbonic  acid  gas  and  ethylamine.  It  com- 
bines with  ammonia,  developing  heat  and  producing  ethylurea 
(page  443). 

The  bodies  which  have  until  now  been  known  as  cyanic  acid 
and  ethyl  cyanate,  are  only  isomerides  of  the  oxygen  com- 
pounds of  cyanogen.  They  should  be  named  isocyanic  acid 
and  isocyanate  of  ethyl.  The  true  cyanic  ether,  (C2H5.O)CN, 
or  rather  a  polymeride  of  that  body,  has  been  obtained  by 
Cloe'z.  It  is  formed  by  the  action  of  cyanogen  chloride  on 
ethylate  of  sodium. 

CNC1      +      Na.OC2H5      =      CN.OC2H5  +  NaCl 

Cyanogen  chloride.          Sodium  ethylate.  Ethyl  cyanate. 

Potassium  hydrate  decomposes  the  true  ethyl  cyanate,  like 
all  other  compound  ethers,  into  alcohol  and  the  corresponding 
potassium  salt  (cyanate). 

ETHYLSULPHURIC,  OR  SULPHOVINIC  ACID. 


H  HO 


This  body  is  an  example  of  an  acid  ether.  It  results  from 
the  substitution  of  a  single  ethyl  group  for  one  atom  of  hydro- 
gen in  sulphuric  acid,  which  is  dibasic. 


ETHYL   CARBONATE.  469 


H) 
P) 


so* 


It  is  formed  by  the  action  of  sulphuric  acid  upon  alcohol. 
The  mixture  of  the  two  bodies  becomes  hot,  and  if  after  cool- 
ing the  liquid  be  diluted  and  saturated  with  barium  carbonate, 
an  abundant  precipitate  of  barium  sulphate  will  be  formed,  and 
a  soluble  salt  of  barium,  the  ethylsulphate,  will  remain  in  solu- 
tion. A  solution  of  ethylsulphuric  acid  may  be  obtained  by 
exactly  decomposing  this  salt  with  dilute  sulphuric  acid. 

By  boiling,  ethylsulphuric  acid  is  decomposed  into  sulphuric 
acid  and  alcohol. 


The  ethylsulphates  are  beautiful  salts  ;  they  are  crystalliz- 
able  and  soluble  in  water. 


Ethyl  Sulphate.— ^5  }  SO*     =     ^5 '^>S02.     This 

body,  which  represents  sulphuric  acid  in  which  the  two  atoms 
of  hydrogen  are  replaced  by  two  ethyl  groups,  is  formed  when 
vapor  of  sulphuric  anhydride  is  passed  into  ether  cooled  in  a 
freezing  mixture  (Wetherill). 

(C2H5)20  +  SO3  =  (C2H5)  W 

It  is  an  oily  liquid  having  an  acrid  taste.     Its  density  is 
1.120.     It  cannot  be  distilled. 

ETHYL  CARBONATE. 

C2H5  )  „. 


Ettling  obtained  this  compound  by  introducing  potassium  or 
sodium  little  by  little  into  ethyl  oxalate  heated  to  130°.  The 
metal  dissolves,  disengaging  carbon  monoxide.  A  brown  mass 
is  obtained,  which  must  be  distilled  with  water.  The  ethyl  car- 
bonate which  passes  over  is  dehydrated  with  calcium  chloride 
and  distilled. 

It  may  also  be  obtained  by  double  decomposition  by  heating 
ethyl  iodide  with  silver  carbonate. 

Ethyl  carbonate  is  a  colorless  liquid,  having  a  pleasant,  ethe- 
real odor ;  its  density  at  0°  is  0.9998,  and  it  boils  at  '125°. 

40 


470  ELEMENTS   OP   MODERN   CHEMISTRY. 

In  the  cold,  ammonia  converts  it  into  ethyl  carbamate,  or 
methane. 

C*H«:0>00       *     NH3    =     C*H5H02>CO     +     C2H5'OH 
Ethyl  carbonate.  Ethyl  carbamate. 

It  yields  urea  and  alcohol  when  heated  to  100°  with  am- 
monia. 

' 


Ethyl  carbonate.  Urea. 

ETHYL  CHLOROCARBONATE. 

OTlSx* 

Dumas  obtained  this  ether  by  passing  chlorocarbonic  gas 
into  alcohol.  Water  is  added  to  the  product  of  the  reaction, 
and  the  insoluble  liquid  is  separated,  dried,  and  distilled. 

PI  PI 

cJ>CO     +     C2R5.0H    =    HC1     +    C2H5o>CO 

Chlorocarbonic  gas.  Ethyl  chlorocarbonate. 

It  is  a  liquid  having  a  pungent,  ethereal  odor.  It  boils  at 
94°.  Hot  water  decomposes  it.  Ammonia  converts  it  into 
ethyl  carbamate,  or  urethane. 


SERIES  OF  SATURATED  HYDROCARBONS. 

C2H2n+2 

To  methane  and  ethane,  which  have  already  been  described, 
are  related  numerous  hydrocarbons  belonging  to  the  same 
series,  CnH2n+2.  They  are  called  saturated  because  no  hydro- 
carbons are  known  in  which  the  number  of  hydrogen  atoms 
exceeds  that  indicated  by  the  preceding  formula.  Again,  the 
hydrocarbons  in  question  can  fix  directly  no  other  atoms.  For 
example,  in  order  that  chlorine  can  enter  into  one  of  their 
molecules,  hydrogen  must  first  be  removed,  and  this  displace- 
ment is  known  to  take  place,  atom  for  atom,  according  to  the 
law  of  substitution.  Thus,  if  chlorine  be  made  to  act  upon 
the  hydrocarbon  C6HU  (hexane),  the  compounds  C*H13C1, 
CGH12C12,  C6H"C18,  maybe  obtained  successively.  Let  us  con- 
sider the  first  of  these  compounds,  C6H18C1.  The  Cl  may  be 
replaced  by  the  group  OH,  and  the  chloride  is  thus  converted 


SATURATED    HYDROCARBONS.  4*71 

into  an  alcohol.     For  this  purpose  the  chloride  is  caused  to 
react  with  a  silver  salt,  the  acetate,  for  example,  and  hexyl 
acetate  is  formed  by  double  decomposition. 
C6H13C1     -f     AgC2H302    =     C6H13.C2H302     +     AgCl 

Hexlyl  chloride.  Silver  acetate.  Hexyl  acetate. 

Boiling  potassium  hydrate  will  transform  this  ether  into 
hexyl  hydrate. 
C6H13.C2H302     +     KOH    =    KC2H302     +     C6H13.OH 

Hexyl  acetate.  Potassium  acetate.  Hexyl  hydrate. 

This  series  of  reactions  permits  of  the  successive  transforma- 
tion of  any  hydrocarbon  of  the  saturated  series  into  a  chloride, 
an  acetate,  and  a  hydrate,  and  the  latter  is  the  alcohol  corre- 
sponding to  the  hydrocarbon.  The  following  is  the  series  of 
saturated  hydrocarbons : 

CH*      methane. 
C2H<5     ethane. 
C3H8     propane. 

butanes. 

pentanes, 

hexanes, 
C7I116   heptanes, 
C8H!8    octanes. 
C9!!20    nonanes. 
C10H23  deoanes,  etc. 

All  of  these  hydrocarbons,  after  the  fourth  of  the  series,  up 
to  the  term  C16H3*,  have  been  obtained  from  petroleum  and 
the  products  of  distillation  of  bitumen  and  peat.  Towards 
the  close  of  the  distillation,  when  the  temperature  passes  above 
300°,  the  products  which  distil  condense  to  a  solid  mass  on 
cooling.  When  properly  purified,  this  solid  forms  a  colorless, 
translucent  mass,  which  has  received  the  name  paraffin.  It 
is  probably  a  mixture  of  several  hydrocarbons  of  the  series 
CnH2ll+2.  Its  point  of  fusion  varies  between  45  and  65°. 

All  of  the  compounds  belonging  to  this  series  cannot  be 
described  here,  but  we  may  briefly  consider  their  constitution. 

The  third  member  of  the  series,  propane,  C3H8,  has  the  con- 
stitution indicated  by  the  formula  CH3-CH2-CH3.  It  is  a  gas 
which  liquefies  at  — 1*7°. 

Its  superior  homologue,  butane,  C4H10,  has  the  constitution 
CH3-CH2-CH2-CH3,  and  can  be  obtained  by  the  action  of 
zinc  or  sodium  on  ethyl  iodide. 

2C2H5I  +  Na2  =  2NaI  +  C*H10 

It  is  a  colorless  gas,  condensable  at  -j-l°.     But  we  have 


472  ELEMENTS    OF    MODERN    CHEMISTRY. 

here  a  remarkable  instance  of  isomerism.  There  is  another 
butane,  isomeric  with  the  preceding,  and  having  the  consti- 

CH3 

tution  expressed  by  the  formula  CH3-CH<^nTT3,     It  is  tri- 

LtL 

methyl-methane,  CH(CH3)3,  while  normal  butane  is  dimethyl- 
ethane,  C2H*(CH3/,  or  propyl-methane,  CH3(C3H7).  The  sig- 
nification of  these  words  and  formulae  is  evident.  Trimethyl- 
methane  is  methane,  CH4,  in  which  three  atoms  of  hydrogen 
are  replaced  by  three  methyl  groups.  The  difference  in  the 
atomic  grouping  is  attended  by  a  difference  in  properties. 
Trimethyl-niethane  is  a  gas  which  condenses  only  at  —  17°. 

The  succeeding  terms  of  the  series  present  isomerisms  of 
the  same  kind,  but  much  more  numerous  as  their  molecular 
complication  is  greater.  They  need  not  be  described  here,  since 
the  same  general  principles  apply  to  all. 

SERIES   OF  ALCOHOLS. 

Ethyl  alcohol,  of  which  the  more  important  compounds 
have  been  briefly  described,  is  not  the  only  product  of  the  fer- 
mentation of  saccharine  liquids.  Other  alcohols  are  formed  in 
small  quantity  in  this  reaction,  which  is  conducted  on  an  exten- 
sive scale  in  the  arts.  Among  these  alcohols  of  fermentation 
are  the  following  : 

Propyl  alcohol,  or  propyl  hydrate,  C8H7.T)H 
Butyl  alcohol,  or  butyl  hydrate,  C*H9.OH 
Amyl  alcohol,  or  amyl  hydrate,  C5Hn.OH 
Hexyl  alcohol,  or  hexyl  hydrate,  C6H13.OH 
Heptyl  alcohol,  or  heptyl  hydrate,  C7Hl&.OH 

To  each  of  these  alcohols  correspond  numerous  ethereal  com- 
pounds in  which  the  groups  propyl,  C3H7,  butyl,  C4H9,  amyl, 
C5HU,  etc.,  are  substituted  for  the  hydrogen  of  the  hydracids 
and  oxacids.  To  each  of  those  alcohols  correspond  also  an 
aldehyde  and  an  acid,  just  as  ordinary  aldehyde  and  acetic  acid 
correspond  to  ordinary  alcohol  or  ethyl  hydrate. 
CH3  CH3  CH» 

CH2.0H  CHO  CO.OH 

Alcohol.  Aldehyde.  Acetic  acid. 

CH2-CH3  CH2-CH8  CH2-CH3 

CR2.0H  CHO  CO.OH 

Propyl  alcohol.         Propyl  aldehyde.  Propionic  acid. 

C3H7 


CR20H  CHO  CO.OH 

Butyl  alcohol.  Butyric  aldehyde  Butyric  acid. 


SERIES   OF   ALCOHOLS.  473 

All  of  these  alcohols  contain  a  group  CH2.OH  united  to  a 
group  or  radical,  CnH2n+1.  When  they  are  converted  by  oxi- 
dation into  aldehydes  and  acids,  the  group  CH2.OH  is  trans- 
formed into  a  group  CHO,  characteristic  of  the  aldehydes,  or 
a  group  CO. OH,  characteristic  of  the  acids.  These  alcohols 
are  said  to  be  primary.  Beginning  with  butyl  alcohol,  the 
primary  alcohols  may  have  several  isomeric  modifications,  as 
will  be  seen  shortly.  Independently  of  the  primary  alcohols, 
there  are  others,  isomeric  with  the  preceding,  but  distinguished 
from  them  by  the  fact  that  they  do  not  yield  corresponding 
aldehydes  and  acids  when  oxidized.  These  iso-alcohols  are 
divided  into  secondary,  which  contain  the  group  CH.OH,  and 
tertiary,  which  contain  the  group  C.OH  (Kolbe).  Without 
entering  into  the  details  of  this  subject,  we  may  cite  two 
examples : 

1 .  By  the  action  of  nascent  hydrogen  upon  acetone,  Friedel 
obtained  isopropyl  alcohol. 

Gils  CH3 

CO     +     H*    =     CH.OH 

CH3  CH3 

Acetone.  Isopropyl  alcohol. 

By  oxidation  of  this  iso-alcohol,  which  is  a  secondary  alcohol 
(containing  the  group  CH.OH),  acetone  is  again  reproduced. 

CH3  CH3 

CH.OH     +      0    =  :    H20     +     CO 


CH3 


CH3 


2.  Boutlerow  discovered  an  isomeride  of  butyl  alcohol,  and 
named  it  tertiary  butyl  alcohol;  its  constitution  is  expressed  by 
the  formula 

CH3 

CH3-C.OH 
CH3 

This  alcohol  contains,  as  is  seen,  the  group  C.OH.  It  yields 
neither  aldehyde  nor  acid  by  oxidation. 

In  the  primary  alcohols,  the  OH  is  united  to  a  C  which  is 
combined  with  only  one  other  carbon  atom ;  in  the  secondary 
alcohols,  to  a  C  united  to  two  other  carbon  atoms  ;  while  in  the 
tertiary  alcohols,  the  C  to  which  the  hydroxyl  is  attached  is 
joined  to  three  other  atoms  of  carbon. 

40* 


474  ELEMENTS    OF    MODERN    CHEMISTRY. 

Propyl  Alcohol,  C3H80  =  CH3-CH2-CH2.OH.—  This  was 

discovered  by  Chancel  in  the  oily  liquid  remaining  after  the  dis- 
tillation of  brandy.  It  is  a  spirituous  liquid,  boiling  at  98°. 
Its  iodide,  C3H7I,  boils  at  104.5°  (I.  Pierre  and  Puchot). 

The  isopropyl  alcohol  of  Friedel  is  formed  under  the  circum- 
stances just  indicated.  Its  constitution  is  expressed  by  the 
formula 

CH3-CH.OH-CH3 

It  boils  at  86°.  When  propylene  gas  is  heated  with  hydri- 
bodic  acid,  isopropyl  iodide,  C3H7I,  is  obtained,  boiling  at  92°. 

C3H6     +     HI    =     C3H'I 

Propylene.  Isopropyl  iodide. 

Silva  has  described  numerous  derivatives  of  isopropyl  alco- 
hol. 

Butyl  Alcohols,  C*H100.  —  The  constitution  of  the  butyl 
alcohol  of  fermentation,  which  is  a  primary  alcohol,  is  expressed 

riTT3 

by  the  formula  pg3>CH-CH2.OH.    It  is  isobutyl  alcohol. 

In  1852,  Wurtz  obtained  it  from  the  fusel-oil  from  the  rec- 
tification of  beet-root  alcohol.  It  is  a  colorless  liquid,  having 
a  penetrating  odor  analogous  to  that  of  amyl  alcohol,  but  more 
spirituous.  It  dissolves  in  10.5  times  its  volume  of  water.  It 
boils  at  109°,  and  yields  on  oxidation  an  acid  isomeric  with 
butyric  acid  and  called  isobutyric. 

It  may  be  regarded  as  ordinary  alcohol  in  which  two  atoms 
of  hydrogen  are  replaced  by  two  methyl  groups. 
CH3  CH(CH3)2 

CH2.OH  CH2.OH 

Alcohol.  Isobutyl  alcohol. 

Lieben  discovered  normal  butyl  alcohol,  isomeric  with  the 
alcohol  of  fermentation,  and  which  yields  butyric  aldehyde  and 
butyric  acid  by  oxidation.  He  obtained  this  alcohol  by  the 
action  of  sodium  amalgam  in  presence  of  water  on  butyral 
(butyric  aldehyde). 


i          +    H2    =       i 
CHO  CH2.OH 

Butyral.  Normal  butyl  alcohol. 


De  Luynes  obtained  another  isomeride  of  butyl  alcohol  by 
the  reduction  of  erythrite  (page  565).  This  alcohol  is  second- 
ary, having  the  constitution  CH3-CH2-CH(OH)-CH3.  It 


SERIES   OF   ALCOHOLS.  475 

boils  at  116.9°  (Lieben).     The  corresponding  iodide,  CH3- 
CH2-CHI-CH3,  boils  at  118°.     It  is  formed  by  the  following 
reaction : 
C*H1004    +     7HI    ==       OH9I      +     4H20     +     3I2 

Erythrite.  Secondary  butyl  iodide. 

The  tertiary  butyl  alcohol  discovered  by  Boutlerow  has  re- 
ceived the  name  trimethylcarbinol,  on  account  of  its  constitu- 
tion, which  has  already  been  indicated.  It  is  a  well-crystallized 
compound,  melting  between  20  and  25°. 

In  conclusion,  four  alcohols  are  known  having  the  composi- 
tion C4H100,  and  presenting  a  remarkable  instance  of  isomer- 
ism.  Their  constitutions  are  again  indicated  in  the  following 
formulae : 

CH3  CH3  CH3  CH3 

CH2  CH3-CH  CH2  CH3-C.OH 

CH2  CH2.OH  CH.OH  CH3 

CH2.OH  CH3 

Normal  primary        Primary  isobutyl  Secondary  butyl  Tertiary  butyl 

butyl  alcohol,      alcohol  (fermentation).  alcoliol.  alcohol. 

(Lieben.)                      (Wurtz.)  (De  Luynes.)  (Boutlerow.) 

PTJ3 

Amyl  Alcohol  of  Fermentation—  C5H12O  =  CH3>CH~ 

CH2-CH2.OH.  This  is  the  most  abundant  constituent  of 
fusel-oil  from  beet-root  and  potatoes,  as  well  as  of  that  from 
the  marc  of  grapes,  from  whiskey,  etc.  These  products  are 
only  the  residues  of  the  distillation  of  alcohol  from  various 
sources. 

Amyl  alcohol  is  a  colorless  liquid,  having  a  rather  unpleasant 
odor.  It  boils  at  132°.  Its  density  at  15°  is  0.8184.  It  is 
nearly  insoluble  in  water.  It  turns  the  plane  of  polarization 
to  the  left.  There  is,  nevertheless,  an  amyl  alcohol  which  has 
no  action  upon  polarized  light,  and  which  Pasteur  has  named 
inactive  amyl  alcohol.  The  latter  boils  at  130°.  It  is  iso- 
meric  with  the  amyl  alcohol  of  fermentation,  from  which  it 
differs  in  physical  properties,  but  presents  the  same  composi- 
tion and  the  same  chemical  properties.  It  is  a  case  of  physical 
isomerism. 

When  submitted  to  the  action  of  zinc  chloride,  amyl  alcohol 
is  converted  into  amylene  and  polymerides  of  that  body  (di- 
amylene,  C10H20,  triamylene,  C15H:io). 

C5H120    =     C5H10    +     H20 

Amyl  alcohol.  Amylene. 


476  ELEMENTS   OF   MODERN    CHEMISTRY. 

By  oxidation,  amyl  alcohol  yields  valeric  aldehyde  and  val- 
eric acid. 

C5H120  +  O   =  H20  +  C5H100 

Valeral,  or  valeric  aldehyde. 

C5H120  +  O2  =  H20  +  C5H1002 

Valeric-  acid. 

The  numerous  amylic  ethers  cannot  be  described  here. 

Amyl  oxide,  (C5Hn)20,  is  a  colorless  liquid,  having  a  suave 
odor,  and  boiling  at  176°  (Williamson). 

Amyl  chloride,  C5HUC1,  is  a  colorless  liquid  of  an  aromatic 
odor,  boiling  at  102°. 

Amyl  iodide,  C5HUI.  is  a  colorless  liquid,  which  becomes 
brown  when  exposed  to  the  light.  Density  at  0°,  1.4676. 
Boiling-point,  147°. 

Isomerides  of  Amyl  Alcohol.  —  At  least  five  alcohols  are 
known  having  the  composition  of  amyl  alcohol.  Independ- 
ently of  the  normal  alcohol  CH3-CH2-CH2-CH2-CH2.OH 
(boiling-point,  137°),  which  Lieben  obtained  by  the  action  of 
nascent  hydrogen  on  valeral  (valeric  aldehyde),  and  the  alco- 
hol of  fermentation  which  has  just  been  described,  and  which 
may  be  called  isopropyl-ethyl  alcohol, 


there  are  three  others  having  the  composition  C5H120.  The 
most  important  is  the  compound  which  is  generally  called  hy- 
drate of  amylene,  because  it  breaks  up  very  readily  into  water 
and  amylene.  It  is  a  tertiary  alcohol  of  the  form 


Its  corresponding  iodide  is  formed  by  direct  union  of  hydri- 
odic  acid  and  the  amylene  prepared  by  the  action  of  zina 
chloride  upon  amyl  alcohol  of  fermentation  (A.  Wurtz). 

CH10  -j-  HI  =  C5H"I 

This  iodide  boils  at  129°.  By  treating  it  with  water  and 
silver  oxide,  Wurtz  obtained  the  alcohol  which  he  named 
hydrate  of  amylene.  The  latter  liquid  boils  at  105°.  It  is 
decomposed  by  heat  alone  into  amylene  and  water,  according 
to  the  equation  before  given.  The  other  isomerides  of  amyl 
alcohol  need  not  be  described. 


SERIES   OF   ALCOHOLS.  47*7 

Hexyl  and  Heptyl  Alcohols.  —  Faget  announced  that  the 
residues  from  the  distillation  of  fusel-oil  from  fermented  grape- 
juice  contained  a  small  quantity  of  hexyl  (C6H140)  and  heptyl 
(C7H160)  alcohols,  but  such  alcohols  have  not  been  refound 
in  that  product. 

Normal  hexyl  alcohol  has  been  obtained  from  the  volatile 
oil  of  the  seeds  of  Heracleum  giganteum,,  an  oil  which  contains 
butyrate  of  hexyl,  C6H13.C4H702.  The  normal  alcohol  boils 
at  157-158°. 

Normal  heptyl  alcohol,  C7H160,  has  been  prepared  by  the 
action  of  nascent  hydrogen  on  oenanthic  aldehyde  C7H140. 
It  boils  at  175-17*7°,  and  has  an  aromatic  odor. 

Octyl  Alcohols,  C8H18O.  —  Normal  octyl  alcohol  may  be  ex- 
tracted from  the  seeds  of  Heracleum  spondylium  and  Hera- 
cleum giganteum,  in  which  octyl  acetate,  C8H17.C2H302,  exists. 
This  ether  is  separated  and  decomposed  by  boiling  potassium 
hydrate.  Its  boiling-point  is  between  190  and  192°. 

Bouis  discovered  secondary  octyl  alcohol.  By  boiling  one 
of  the  acids  produced  by  the  saponification  of  castor-oil,  rici- 
nolic  acid,  with  potassium  hydrate,  Bouis  decomposed  it  into 
sebacic  acid  and  a  new  secondary  alcohol.  This  is  octyl  alco- 
hol, C8H180,  a  colorless  liquid  having  a  pleasant,  aromatic  odor, 
and  boiling  at  178°.  The  following  equation  explains  its 
formation  : 


=  K2C10H1604  +  C8H180  -f  H2 

Kicinolic  acid.  Potassium  sebate.       Octyl  hydrate. 

Cetyl  Alcohol.  —  The  concrete  portion  of  an  oil  which  fills 
the  cranial  sinuses  of  the  sperm-whale  is  called  spermaceti. 
When  properly  purified  it  occurs  in  beautiful  pearly  plates, 
fusible  at  49°.  It  is  a  compound  ether  of  which  the  nature 
was  recognized  by  Chevreul  in  1823.  By  submitting  it  to  the 
action  of  potassium  hydrate,  that  chemist  decomposed  it  into 
palmitic  acid  and  a  new  alcohol  which  he  called  ethal,  to  denote 
its  relations  with  alcohol  and  ether.  It  is  now  called  cetyl 
alcohol,  or  cetyl  hydrate. 


Cetyl  palmitate.  Cetyl  hydrate.     Potassium  palmitate. 

It  belongs  to  the  same  homologous  series  as  the  preceding 
alcohols. 

Alcohols  from  Wax.  —  The  most  complex  alcohols  of  the 
series  under  consideration  were  obtained  from  wax  by  Brodie. 


478  ELEMENTS   OF   MODERN   CHEMISTRY. 

Ordinary  beeswax  is  a  mixture  of  a  fatty  acid,  C27H5402,  called 
cerotic  acid  (cerin),  and  a  compound  ether,  the  palmitate  of 
myricyl  (inyricin).  The  two  bodies  are  separated  by  alcohol, 
which  readily  dissolves  the  first,  but  in  which  the  second  is  but 
slightly  soluble.  By  boiling  the  palmitate  of  myricyl  with 
potassium  hydrate,  it  breaks  up  into  palmitic  acid  and  hydrate 
of  myricyl,  or  myricyl  alcohol,  C^H^O. 

Chinese  wax  is  a  compound  ether ;  it  is  cerotate  of  ceryl,  and 
may  be  decomposed  by  caustic  potassa  into  cerotic  acid  and 
ceryl  hydrate,  or  ceryl  alcohol,  C27H560.  The  hydrates  of  cetyl 
and  ceryl  are  solid  bodies. 

ALLYL  ALCOHOL. 

C8H5.0H  =  CH^CH-CH2.OH 

All  of  the  alcohols  thus  far  considered  belong  to  the  series 
CnH2n+20.  There  are  other  monatomic  alcohols  which  belong 
to  different  series,  that  is,  in  which  there  are  different  relations 
between  the  number  of  hydrogen  atoms  and  the  number  of 
carbon  atoms.  Among  these  other  alcohols,  the  most  impor- 
tant is  allyl  alcohol,  or  hydrate  of  allyl,  so  named  because  it  is 
closely  related  to  the  essential  oil  of  garlic,  which  is  allyl  sul- 
phide. Another  natural  oil,  that  of  mustard,  is  sulphocyanate 
of  allyl. 

C3H5.OH  (C3H5)2S  C3H5.CNS 

Allyl  hydrate.  Allyl  sulphide.  Allyl  sulphocyanate. 

Hofmann  and  Cahours  prepared  allyl  hydrate  and  a  great 
number  of  its  derivatives  artificially  by  the  aid  of  allyl  iodide, 
C3H5I,  which  is  formed  when  glycerin  is  acted  upon  by  iodide 
of  phosphorus,  P2I*  (Berthelot  and  de  Luca).  This  iodide, 
whose  relations  to  allyl  alcohol  are  the  same  as  those  of  ethyl 
iodide  to  ordinary  alcohol,  is  a  colorless  liquid,  having  a  slightly 
pungent,  garlicky  odor,  and  boiling  at  101°. 

When  heated  with  mercury  and  concentrated  hydrochloric 
acid,  it  yields  pure  propylene  gas  (Berthelot). 

2C3H5I  +  2HC1  +  4Hg  =  2C3H6  -f  Hg2!2  -f  Hg2Cl2 

Allyl  iodide.  Propylene. 

Tollens  and  Henninger  discovered  a  very  simple  process  for 
the  preparation  of  allyl  alcohol.  It  consists  in  heating  formic 
acid,  or  oxalic  acid,  from  which  the  former  acid  is  produced, 
with  glycerin  to  220°.  The  allyl  alcohol  which  distils  is 


COMPOUND   AMMONIAS.  479 

washed  with  a  concentrated  solution  of  potassium  carbonate, 
and  rectified  over  lime.  In  this  reaction,  a  monoformine  of 
glycerin  is  first  produced,  and  this  decomposes  at  220°  into 
carbon  dioxide,  water,  and  allyl  alcohol. 

fO.CHO 

C3R5  J  OH      =   CO2    +    H20    +    C3H5.0H 
(OH 

Monoformine  of  glycerin.  Allyl  alcohol. 

It  will  be  seen  that  the  reaction  is  really  a  reduction. 

Allyl  alcohol  is  a  colorless  liquid,  boiling  at  97°,  and  having 
a  pungent,  alcoholic  odor.  It  dissolves  in  all  proportions  of 
water.  Density  at  13°,  0.86. 

Allyl  alcohol  is  an  unsaturated  compound  ;  it  can  fix  directly 
two  atoms  of  hydrogen,  chlorine,  or  bromine,  or  one  molecule 
of  hydrobromic  acid,  etc. 

Acrolein,  a  volatile  liquid  that  is  formed  in  the  distillation 
of  fatty  bodies,  is  the  aldehyde  of  allyl  alcohol.  Acrylic  acid 
is  the  corresponding  acid. 


COMPOUND  AMMONIAS,  OR  AMINES. 

Wurtz  gave  these  names  to  the  basic  combinations  resulting 
from  the  substitution  of  alcoholic  radicals,  such  as  methyl, 
ethyl,  etc.,  for  the  hydrogen  of  ammonia.  This  substitution 
may  be  more  or  less  complete ;  1,  2,  or  3  atoms  of  hydrogen 
may  be  replaced  by  as  many  alcoholic  groups.  Hence  there 
are  various  classes  of  amines ;  they  are  designated  by  the  names 
primary,  secondary,  and  tertiary. 

PRIMARY   AMINES.          SECONDARY  AMINES.         TERTIARY   AMINES. 

H)  CH3)                         CHn                         CHM 

H  V  N  H  \  N                    CH3  [  N                    CH3  [  N 

Hj  HJ                            Hj                         CH3J 

Ammonia.  Methylamine.  Dimethylamine.  Trimethylamine. 

C2H5)  C2H5)  C2H5) 

H  [  N  C2H&  I  N  C2H5  I N 

H  j  H  J  C2H5  J 

Ethylatnine.  Diethylamine.  Triethylamine. 

Lastly,  bases  are  known  which  are  the  most  energetic  of 
all,  and  may  be  considered  as  derived  from  the  hypothetical 
hydrate  of  ammonium  by  the  substitution  of  alcoholic  radicals 
for  4  atoms  of  hydrogen. 


480  ELEMENTS   OF    MODERN    CHEMISTRY. 


} 

C2H5  (  XT  nw 
C2H5    N'OH 
C2H5J 
Hydrate  of  tetrethylanimoniiim. 

The  latter  ammonia-ted  bases,  as  well  as  the  secondary  and 
tertiary  amines,  were  discovered  by  Hofmann. 

In  the  amines,  nitrogen  acts  as  a  triatomic  element  or  tri- 
valent;  but  it  may  assume  two  other  atomicities.  In  sal- 
ammoniac,  it  is  pentatomic,  and  it  may  play  precisely  the  same 
part  in  the  amines. 


7 

x\ 

C2R5         C2R5 

Triethylaniine. 

Cl 
H          H 

*<  X 
N 

x\ 

H      H 

AlnmoniTim 
chloride. 

(OH)' 
(C2H6)'           (C2R5)' 

<:  x 

N 

x\ 

(C2H6)'       (C2II5)' 
Tetrethylammonium 
hydrate. 

x\ 

H      H 

Ammonia. 

Related  to  the  amines  are  various  organic  combinations 
which  have  the  same  constitution,  but  in  which  the  nitrogen 
is  replaced  by  an  analogous  element,  such  as  phosphorus, 
arsenic,  or  antimony.  A  great  number  of  these  bodies  have 
been  discovered,  of  which  the  more  important  are 


C2H5  ) 

C2H5      p'"  C2H5  L  As'"  C*H6  \  Sb 

C2I15  )  C2H5  j  C2II5  J 

Triethylphosphine.  Triethylarsine.  Triethylstibine. 

The  nitrogenized  bases  that  have  just  been  considered  belong 
either  to  the  type  NX3  or  to  the  type  NX5.  A  new  class  of 
compounds  has  recently  been  discovered,  belonging  to  the  type 
N2X4. 

It  is  evident  that  the  group  NX2  (amidogen)  cannot  exist 
in  the  free  state.  If  it  could  be  isolated,  it  would  probably 
combine  with  itself,  forming  a  double  molecule 

NH2 


Fischer  has  made  known  several  substituted  derivatives  of 
this  body,  N2H4,  which  he  names  hydrazine.  He  has  described 
ethylhydrazine,  NH2-NH(C2H5).  It  is  a  base  soluble  in 
water,  and  having  an  ammoniacal  odor  ;  its  hydrochloride  con- 
tains N2H3(C2H5).2HC1. 

The  compound  ammonias  cannot  all  be  described  here  ;  we 
need  only  consider  the  more  important. 


METHYLAMINE.  481 


METHYLAMINE. 

CH3) 

CH^N  =r       H  [  N 
HJ 

This  body  may  be  prepared  by  boiling  together  potassium 
hydrate  and  methyl  cyariate  or  cyanurate,  and  passing  the 
vapors  which  are  disengaged  into  dilute  hydrochloric  acid  ; 
methylauiine  hydrochloride  is  thus  formed. 

PfK  CR3 

2KOH  =   K2C°3 


Methyl  cyanate.  Methyl  amine. 

The  solution  is  evaporated  to  dryness,  and  the  residue  fused 
and  allowed  to  cool  ;  it  is  then  mixed  with  double  its  weight 
of  powdered  quick-lime,  and  the  mixture  gently  heated.  The 
methylamine  disengaged  may  be  collected  over  mercury. 

It  is  a  colorless  gas,  which  condenses  to  a  light  liquid  at  a 
temperature  a  few  degrees  below  0°.  It  is  inflammable,  and 
burns  with  a  pale  flame.  Its  odor  is  strongly  ammoniacal  and, 
at  the  same  time,  recalls  that  of  the  sea.  It  is  the  most  solu- 
ble of  all  gases.  1  volume  of  water  at  12.5°  absorbs  1153 
volumes  of  methylamine.  The  aqueous  solution  possesses  the 
odor  of  the  gas,  a  caustic  taste,  and  a  strong,  alkaline  reaction. 
Like  ammonia,  it  precipitates  the  oxides  from  solutions  of  the 
metallic  salts. 

If  a  solution  of  methylamine  be  added  to  a  solution  of  cupric 
sulphate,  a  light-blue  precipitate  is  first  formed,  but  disappears 
if  an  excess  of  methylamine  be  added,  yielding  a  beautiful  blue 
solution. 

Methylamine  Hydrochloride,  CH5N.HC1,  differs  from  am- 
monium chloride  by  its  solubility  in  boiling  alcohol,  from  which 
it  is  deposited  on  cooling  in  large,  colorless,  deliquescent  plates. 
With  platinic  chloride  it  forms  a  yellow  precipitate,  soluble  in 
boiling  water,  from  which  it  crystallizes  in  golden-yellow  scales. 

It  is  a  chloroplatinate,  (CH5N.HCl)2.PtCl4. 

DIMETHYLAMINE,  TRIMETHYLAMINE,  TETRA- 
METHYLAMMONIUM   HYDRATE. 

These  compounds  were  discovered  by  Hofmann. 
Dimethylamine,  (CH3)2NII,  is  a  combustible  gas  which  lique- 
fies at  8°. 

v  41 


482  ELEMENTS    OF    MODERN    CHEMISTRY. 

Trimethylamine,  (CH3)3N,  exists  ready  formed  in  the  CTieno- 
podium  vulvaria^  in  the  flowers  of  Cratsegus  oxyacantha,  in 
herring-brine,  in  cod-liver  oil,  and  in  coal-gas  tar.  Vincent 
extracts  large  quatities  of  it  from  the  residues  of  the  distilla- 
tion of  fermented  beet-juice. 

At  ordinary  temperatures  it  is  a  gas;  it  liquefies  at  9°.     It  is 
very  soluble  in  water  and  in  alcohol.    It  has  a  strong,  ammoniacal 
odor,  and  an  intense,  alkaline  reaction.    It  unites  directly  with 
methyl  iodide,  forming  the  iodide  of  tetramethylanimonium. 
(CH3/N  +  CtPI  =  (CH3/NI 

This  iodide  possesses  all  the  appearances  of  a  salt.  It  is 
soluble  in  water,  and  the  solution  treated  with  silver  oxide  yields 
silver  iodide  and  tetramethylanimonium  hydrate. 

2(CH3)4NI  -f  Ag20  +  H20  =  2AgI  +  2(CH3)4N.OH 

The  latter  body  is  very  soluble  in  water,  and  the  solution  is 
caustic.  When  submitted  to  dry  distillation,  it  decomposes  into 
trimethylamine  and  methyl  alcohol. 

(CH3)4N.OH  =  CH3.OH  +  (CH3)3N 

ETHYLAMINE. 


C2H'N    =         H  \  N 
HJ 

Ethylamine  is  prepared  by  a  process  analogous  to  that  which 
yields  methylamine  ;  cyanate  or  cyanurate  of  ethyl  is  decom- 
posed with  boiling  potassium  hydrate,  and  the  vapors  are  con- 
densed in  very  dilute  hydrochloric  acid.  The  dry  ethylamine 
hydrochloride  is  then  treated  with  quick-lime  (A.  Wurtz). 

Another  process  has  been  indicated  by  Hofmann.  It  consists 
in  causing  ammonia  to  react  upon  the  bromide  or  iodide  of 

ethyl. 

H)  eras} 

C2H&Br    +    H  \  N    =          H  >  N.HBr 
HJ  HJ 

Ethylamine  hydrobromide. 

Ethylamine  is  a  light,  mobile,  colorless  liquid;  it  boils  at 
18.7°.  Its  odor  is  strong  and  exactly  resembles  that  of  am- 
monia. 

Ethylamine  is  inflammable.  It  mixes  with  water,  alcohol, 
and  ether  in  all  proportions.  Its  aqueous  solution  is  caustic, 
and  precipitates  most  of  the  metallic  salts  like  solution  of  am- 


ETHYLPHOSPHINES.  483 

monia,  and,  like  the  latter,  redissolves  cupric  hydrate,  forming 
a  blue  liquid. 

Ethylamine  Hydrochloride,  C2HYN.HC1.—  This  salt  crys- 
tallizes in  large,  deliquescent  plates,  soluble  in  absolute  alcohol. 
Its  aqueous  solution  yields  with  platinic  chloride  a  precipitate 
composed  of  yellow  scales,  soluble  in  boiling  water,  and  consti- 
tuting a  chloro-platinate,  (C2H7N.HCl)2.PtCl4. 

DIETHYLAMINE,  TRIETHYLAMINE,  TETRETHYL- 
AMMONIUM  HYDRATE. 
C2H5^ 

Diethylamine,  C2H5  v  N,  was  obtained  by  Hofmann  by  heat- 

H  ) 

ing  ethylamine  with  ethylbromide,  and  decomposing  the  die- 
thylamine  hydrobromide  formed  by  an  alkali. 


N.HBr 
H  H 

Ethylamine.  Diethylamine  hydrobromide. 

The  free  base  is  a  liquid  having  an  ammoniacal  odor  and 
boiling  at  57.5° 

Triethylamine  may  be  formed  by  the  action  of  ethyl  bro- 
mide on  diethylamine  ;  triethylamine  hydrobromide  is  formed, 


C2H5  >-  N.HBr,  from  which  alkalies  cause  the  disengagement 

C2H5) 

of  triethylamine,  a  colorless  liquid,  boiling  at  91°  ;  its  odor 

is  ammoniacal  and  its  reaction  strongly  alkaline. 

Tetrethylammonium  Hydrate.  —  When  a  mixture  of  ethyl 
iodide  and  triethylamine  is  heated  on  a  water-bath,  the  two 
bodies  combine,  forming  the  compound  which  Hofmann  has 
named  tetrethylammonium  iodide. 

C2H5I        +        (C2H5)3N        =        (C2H5)4N.I 

Ethyl  iodide.  Triethylamine.  Tetrethylammonium  iodide. 

When  this  is  treated  with  silver  oxide  and  water,  it  yields 
silver  iodide  and  tetrethylammonium  hydrate,  (C2H5)4N.OH,  a 
powerful  base,  which  is  crystallizable  and  soluble  in  water.  Its 
energy  is  comparable  to  that  of  potassium  hydrate. 

ETHYLPHOSPHINES. 

Primary,  secondary,  and  tertiary  ethylphosphines  are  known, 
as  well  as  the  compounds  of  tetrethylphosphonium. 


484  ELEMENTS   OF   MODERN   CHEMISTRY. 


H  |  P'"  C2H5     P'"  C2H5  •  P'"  p25     P- 

HJ  HJ 


Ethylphosphine.    Diethylphosphine.  Triethylphosphine.  Tetrethylphosphonium. 
(Primary.)  (Secondary.)  (Tertiary.) 

The  first  two  have  been  recently  discovered  by  Hofmann.  The 
third  is  due  to  an  admirable  research  of  Hofmann  and  Cahours, 
who  obtained  it  by  the  action  of  phosphorus  trichloride  on  zinc 
ethyl. 
2PC13     +     3[Zn(C2H5)2]     =     2[P(C2H5)3]      -f      SZnCl2 

Zinc  ethyl.  Trietbylphosphine. 

The  operation  must  be  conducted  out  of  contact  with  the 
air,  and  the  zinc  ethyl  must  be  diluted  with  anhydrous  ether. 

Monethylphosphine  and  diethylphosphine  are  produced  when 
ethyl  iodide  is  made  to  react  upon  phosphonium  iodide,  PH*I, 
hydriodide  of  hydrogen  phosphide  (page  167),  in  presence  of 
an  excess  of  zinc  oxide. 


2PH*I  +  ZnO  =  2[(C2H5)H2P.HI]  +  Znl2  +  H20 
2C21M  +     PH*I  +  ZnO  ==      (C2H5)2HP.HI    +  Znl2  +  H20 

As  both  reactions  are  accomplished  simultaneously,  both 
phosphines  are  obtained  at  the  same  time.  They  are  separated 
by  the  action  of  water  upon  the  two  hydriodides  which  are 
formed.  That  of  monethylphosphine  is  decomposed  by  water, 
while  that  of  diethylphosphine  is  only  decomposed  by  the  alka- 
lies. It  is  sufficient  then  to  add  water  to  the  product  of  the 
reaction  in  order  to  set  free  the  monethylphosphine  ;  when 
the  latter  has  been  completely  expelled  by  heat,  potassium  hy- 
drate added  to  the  residue  will  cause  the  disengagement  of  the 
diethylphosphine.  These  operations  should  be  conducted  in  a 
current  of  hydrogen. 

Monethylphosphine,  (C2H5)H2P.  —  This  is  a  colorless  liquid, 
lighter  than  water,  in  which  it  is  insoluble,  and  boiling  at  25°. 
It  has  a  most  disagreeable  odor.  It  takes  fire  on  contact  with 
chlorine  or  nitric  acid.  Its  hydriodide  crystallizes  in  beautiful, 
white,  quadrangular  tables. 

Diethylphosphine,  (C2H5)2HP.—  A  colorless  liquid,  lighter 
than  water,  and  boiling  at  85°.  It  is  very  avid  of  oxygen,  and 
sometimes  takes  fire  spontaneously  on  contact  with  the  air. 

Triethylphosphine,  (C2H5)3P.—  This  is  a  colorless  liquid, 
boiling  at  127.5°.  Density  at  15°,  0.812.  It  combines  di- 
rectly with  oxygen,  forming  triethylphosphine  oxide,  (C2H5)3PO. 
The  latter  is  a  crystalline  solid,  very  soluble  in  water  and  in 
alcohol.  It  distils  at  240°. 


PRODUCTS   OF  OXIDATION   OF   ETHYLPHOSPHINES.     485 

When  treated  with  ethyl  iodide,  triethylphosphine  yields 
tetrethylphosphonium  iodide,  (C2H5)*PI,  a  compound  which 
may  be  obtained  in  beautiful  crystals.  When  this  iodide  is 
acted  upon  by  moist  silver  oxide,  it  furnishes  the  corresponding 
hydrate,  which  is  an  energetic  base. 

2[(C2H5)TI]  +  Ag'O  +  H20  =  2AgI  +  2[(C2H5)4P.OH] 

Tetrethylphosphonium  Tetrethylphosphonium 

iodide.  hydrate. 


PRODUCTS   OF   OXIDATION   OF   ETHYLPHOS- 
PHINES. 

When  the  ethylphosphines  are  treated  with  fuming  nitric 
acid  under  suitable  conditions,  they  act  in  a  characteristic  man- 
ner. Monethylphosphine  is  transformed  into  a  dibasic  acid, 
monethylphosphinic  j  diethylphosphine  yields  a  monobasic  acid, 
diethylphosphinic.  Triethylphosphine  yields  an  indifferent 
oxide,  which  has  already  been  mentioned.  Now,  if  it  be  remem- 
bered that  under  the  same  circumstances  hydrogen  phosphide 
furnishes  phosphoric  acid,  it  will  be  seen  that  the  preceding 
oxidation  compounds  may  be  regarded  as  phosphoric  acid,  in 
which  1,  2,  or  3  groups  OH  ,are  replaced  by  as  many  ethyl 
groups. 


CH 

H 

(H 


(OH 
PO^  OH 
I  OH 

Hydrogen  phosphide.  Phosphoric  acid. 

(  C2H*  f  C»H& 

P^H  PO^OH 

(H  (OH 

Monethylphosphine.  Monethylphosphinic  acid. 

f  C2H& 
P  \  C2H5  PO 

(H  (OH 

Diethylphosphine.  Diethylphospliinic  acid. 

(  C2H5  f 

P     C2H5  PO 


Triethylphosphine.  Triethylphosphine  oxide. 

The  compounds  of  arsenic  and  ethyl  are  entirely  analogous 
to  the  phosphines  ;  they  have  already  been  alluded  to.  Besides 
these,  there  are  ethylic  combinations  corresponding  to  cacodyl 
and  its  derivatives. 

41* 


486  ELEMENTS    OF   MODERN   CHEMISTRY. 

ORQANO-METALLIC   COMPOUNDS. 


ZINC-ETHYL. 

Zn//(C2H5)2 

One  of  the  more  important  of  the  compounds  formed  by  the 
union  of  the  metals  with  alcoholic  radicals  is  zinc-ethyl,  dis- 
covered by  Frankland. 

It  is  prepared  by  heating  ethyl  iodide  with  zinc-turnings 
and  a  small  quantity  of  sodium  on  a  water-bath.  Zinc  iodide 
and  zinc-ethyl  are  formed.  When  the  reaction  is  terminated, 
the  product  is  distilled  and  that  portion  collected  which  passes 
above  115°. 

Zinc-ethyl  is  a  colorless,  mobile,  and  highly-refractive  liquid. 
It  has  a  peculiar,  penetrating,  and  very  disagreeable  odor.  It 
boils  at  118°.  It  takes  fire  spontaneously  on  contact  with  the 
air,  burning  with  a  green  flame,  and  producing  white  fumes 
of  zinc  oxide. 

If  water  be  added  to  a  small  quantity  of  zinc-ethyl  contained 
in  a  tube,  a  brisk  effervescence  at  once  takes  place,  and  a  white 
deposit  is  formed.  The  gas  is  ethane,  and  the  deposit  is  zinc 
hydrate. 

Zn(C2H5)2  +  2H20  ==  Zn(OH)2  +  2C2H6 

Zinc-ethyl  will  enter  into  double  decompositions. 

By  the  action  of  phosphorus  trichloride  on  this  body,  Hof- 
mann  and  Cahours  obtained  triethylphosphine  and  zinc  chloride. 

There  is  a  zinc-methyl,  Zn(CH3)2,  corresponding  to  zinc- 
ethyl. 

MERCUR-METHYL  AND  MERCUR-ETHYL. 

These  compounds  were  obtained  by  Frankland  and  Duppa, 
by  the  action  of  methyl  and  ethyl  iodides  on  sodium  amalgam 
(sodium  1,  mercury  500),  in  presence  of  a  small  quantity  of 
acetic  ether. 

Mercur-ethyl  is  a  colorless,  inflammable  liquid,  insoluble  in 
water.  Density,  2.44.  Boiling-point,  158-160°.  It  is  one 
of  the  most  dangerous  bodies  known.  The  inhalation  of  its 
vapor  for  any  length  of  time,  even  in  small  quantity,  will 
produce  fatal  poisoning. 


STANNETHYLS.  487 

Chlorine,  bromine,  and  iodine  instantly  decompose  mercur- 
ethyl  with  formation  of  a  compound  of  mercur-monethyl. 

f   P2TT5  (    P2rr5 

TT™  3  ^  **  I          T2  P2R5T        I         TTo-  J 

Hg  <  Q2jj5      -j-      1  Hg  I  j 

Mercur-ethyl.  Ethyl  iodide.    Mercur-monetliyl  iodide. 

STANNETHYLS. 

The  discovery  of  the  numerous  compounds  of  tin  and  ethyl 
is  due  to  Lbwig.  Their  history  has  been  completed  by  Frank- 
land,  Cahours,  and  Hiche. 

As  the  nomenclature  and  constitution  of  the  stannethyls 
have  already  been  indicated  (page  424),  we  need  only  consider 
a  few  of  these  interesting  compounds. 

Stannodiethyl,  Sn(C2H5)2. — The  iodide  of  this  compound 
is  obtained  when  ethyl  iodide  is  heated  with  tin-filings  to  about 
180°.  This  iodide,  Sn(C2H5)2!2,  purified  by  crystallization  in 
alcohol,  furnishes  free  Stannodiethyl  when  its  solution  is  treated 
with  zinc,  which  removes  the  iodine. 

Stannodiethyl  is  an  oily,  yellow  liquid,  which  does  not  vola- 
tilize without  decomposition.  When  heated  to  150°  it  begins 
to  boil,  but  the  greater  part  of  it  is  decomposed  into  stanno- 
tetrethyl  and  tin. 

2[Sn(C2H5)2]  =  Sn(C2H5)4  +  Sn 

The  iodide  of  Stannodiethyl  crystallizes  in  pale  yellow  needles. 
In  its  solution,  the  alkalies  precipitate  the  oxide  Sn(C2H5)20, 
which  forms  an  amorphous,  white  precipitate,  insoluble  in  water 
and  alcohol,  but  soluble  in  the  alkalies  and  acids  with  which  it 
forms  salts. 

Stannotriethyl  or  Sesquistannethyl,  Sn2(C2H5)6  =  (C2H5)3 
Sn-Sn(C2H3)3. — This  is  formed,  together  with  the  preceding 
compound,  by  the  reaction  of  ethyl  iodide  on  an  alloy  of  tin  and 
sodium.  It  is  separated  by  fractional  distillation ;  it  boils  between 
265  and  270°.  It  plays  the  part  of  a  radical  and  combines 
directly  with  oxygen.  The  oxide  contains  Sn2(C2H5)60  = 
[Sn(C2H3)3]20.  It  combines  with  the  elements  of  water,  form- 
ing a  hydrate,  Sn(C2H5)3.OH,  crystallizable  in  prisms.  These 
crystals  are  fusible  at  44°.  The  oxide  distils  at  272°.  It 
reacts  with  the  acids  to  form  crystallizable  salts. 

[Sn(C2H5)3]20    +    2HN03   =   2[Sn(C2H5)3.N03]    -f-    H20 

Stan notrietliyl  oxide.  Stannotriethyl  nitrate. 


488  ELEMENTS    OF    MODERN    CHEMISTRY. 

The  iodide,  Sn(C2H5)3I,  is  a  liquid  having  a  mustard-like 
odor,  and  distilling  without  decomposition  towards  235-238°. 
Density  at  15°,  1.833. 

Stannotetrethyl,  Sn(C2H5)4. — Colorless  liquid,  almost  odor- 
less, and  boiling  at  181°.     Density,  1.187.     It  is  formed  by 
the  action  of  zinc  ethyl  on  stannodiethyl  iodide. 
Sn(C2H5)2!2     -f     Zn(C2H5)2     =     Sn(C2H5)4     -f     ZnP 

Stannnodiethyl  iodide.  Zinc-ethyl.  Stannotetretbyl. 

It  is  a  saturated  compound,  and  does  not  enter  into  combi- 
nation, but  by  the  action  of  energetic  reagents  it  yields  com- 
pounds of  stannodiethyl  or  stannotriethyl.  Thus,  with  iodine, 
the  following  reaction  takes  place : 

Sn(C2H5)4  +  P  =  Sn(C2H5)3I  -f  C2H5I 


VOLATILE  FATTY  ACIDS  DERIVED 
FROM  THE  ALCOHOLS. 


Modes  of  Formation  and  Constitution.  —  These  acids  result 
from  the  oxidation  of  the  alcohols  of  which  the  principal  com- 
pounds have  been  described.  They  are  formed  in  a  great  num- 
ber of  reactions,  and  many  of  them  exist  already  formed  in 
nature,  either  in  the  free  state  or  in  combination  in  neutral 
fatty  compounds,  that  is,  the  oils  and  fats. 

Their  composition  is  expressed  by  the  general  formula  CnH2n 
O2  ;  they  contain  one  more  atom  of  oxygen  and  two  atoms  of 
hydrogen  less  than  their  corresponding  alcohols. 

Their  principal  modes  of  formation  are  as  follows  : 

1.  By  oxidation  of  an  alcohol  : 

CH40     -j-     O2     =     CH202     4-     H20 

Methyl  alcohol.  Formic  acid. 

2.  By  oxidation  of  an  aldehyde  : 

C2H40     +     0    =     C2H*02 

Aldehyde.  Acetic  acid. 

3.  By  the  decomposition  of  an  organic  cyanide  with  boiling 
potassium  hydrate: 

CH3  OH3 

+  KOH  +  H!O  = 


Methyl  cyanide.  Potassium  acetate. 


VOLATILE   FATTY   ACIDS.  489 

The  acetic  acid  is  formed  in  this  last  reaction,  by  the  union 
of  the  carbon  of  the  cyanogen  group  with  the  oxygen  of  both 
the  potassium  hydrate  and  the  water,  the  hydrogen  of  these 
two  bodies  combining  with  the  nitrogen  of  the  cyanogen  to 
form  ammonia.  It  may  then  be  admitted  that  acetic  acid  con- 
tains a  radical  carbonyl,  CO,  united  on  the  one  hand  with  a 
methyl  group  (that  of  the  methyl  cyanide),  and  on  the  other 
with  a  hydroxyl  group,  OH. 

The  other  acids  of  the  series  possess  an  analogous  constitu- 
tion. 

CH3  C2H5  C3H7  C4H» 

CO.OH  CO.OH  CO.OH  CO.OH  etc. 

Acetic  acid.         Propiouic  acid.  Butyric  acid.  Valeric  acid. 

4.  A  method  of  synthesis,  discovered  by  Wanklyn,  furnishes 
a  direct  support  to  this  theory  of  the  constitution  of  the  fatty 
acids.  That  chemist  realized  the  synthesis  of  acetic  and  pro- 
pionic  acids  by  passing  a  current  of  carbonic  acid  gas  over 
sodium-methyl  and  sodium-ethyl,  organo-metallic  compounds 
which  result  from  the  action  of  sodium  upon  zinc-methyl  and 
zinc-ethyl. 

OTT3 

NaCH»     +     CO.O    =    f 

CO.ONa 

Sodium-methyl.  Sodium  acetate. 


CO.O 

CO.ONa 
Sodium-ethyl.  Sodium  propionate. 

General  Properties.  —  1.  The  volatile  fatty  acids  of  the  series 
CnH2n02  are  monobasic  ;  each  contains  one  atom  of  hydrogen 
which  may  be  replaced  by  an  equivalent  quantity  of  a  metal. 

2.  When  submitted  to  dry  distillation,  many  of  their  salts 
yield  an  acetone  and  a  carbonate. 

CH» 
=         CO         +         CaC03 

CH3 
Calcium  acetate.  Acetone.       Calcium  carbonate. 

3.  The  same  reaction  may  produce  an  aldehyde  and  a  hydro- 
carbon of  the  series  CnH2n  (Chancel). 

C3H7 


Calcium  butyrate.  Butyral,  or  butyric       Propylene. 

aldehyde. 

V* 


490  ELEMENTS   OP   MODERN   CHEMISTRY. 

4.  When  a  mixture  of  a  salt  of  a  fatty  acid  and  a  formate 
is  subjected  to  dry  distillation,  the  principal  product  of  the 
reaction  is  an  aldehyde  (Piria). 

CH3 

CH3-CO.OK         +         H-CO.OK        =          i  +         KXIO3 

CHO 

Potassium  acetate.  Potassium  formate.  Aldehyde. 

5.  The  fatty  acids  are  converted  into  chlorides  by  the  action 
of  phosphorus  pentachloride,  or  oxy  chloride  (Grerhardt). 

C2H300K       +       PGP      =      C2H3O.C1       +      POC13       +       KC1 
Potassium  acetate.  Acetyl  chloride.        Phosphorus 

oxychloride. 

6.  By  the  action  of  these  chlorides  upon  the  salts  of  the 
fatty  acids,  the  anhydrides  of  the  acids  are  formed  (Gerhardt). 

C°H3°}0        +         CTF.OC1        =,        KC.         + 

Potassium  acetate.  Acetyl  chloride.  Acetic  anhydride. 

7.  When  subjected  to  the  action  of  phosphoric  anhydride, 
the  ammonium  salts  of  these  acids  lose  2H20  and  are  con- 
verted into  nitriles  or  cyanogen  ethers  (Dumas,  Malaguti  and 
Le  Blanc,  Frankland  and  Kolbe). 

CH3  CH3 


_L- 

CO.O(NH4)  CN 

Ammonium  acetate.  Acetonitrile. 

(Methyl  cyanide.) 

FORMIC  ACID. 
CH'O2 

This  acid,  which  was  discovered  by  S.  Fischer  in  1760,  in 
red  ants,  is  formed  in  a  great  number  of  reactions,  particularly 
in  the  oxidation  of  methyl  alcohol,  in  the  decomposition  of 
hydrocyanic  acid  by  acids  or  alkalies,  in  the  distillation  of  oxalic 
acid,  and  in  the  oxidation  of  many  organic  matters,  such  as 
starch,  sugar,  etc.  Berthelot  achieved  its  direct  synthesis  by 
heating  carbon  monoxide  for  a  long  time  to  100°  in  sealed 
flasks  containing  a  concentrated  solution  of  potassium  hydrate. 

CO  +  KOH  =  HCO.OK 

Potassium  formate. 

Preparation.  —  Starch,  manganese  dioxide,  and  dilute  sul- 
phuric acid  may  be  boiled  together  in  a  capacious  retort,  and 
the  acid  liquid  which  condenses  in  the  receiver  saturated  with 
lead  carbonate.  Lead  formate  is  thus  obtained,  and  is  purified 


FORMIC   ACID.  491 

by  crystallization.  To  obtain  formic  acid,  the  salt  is  heated  in 
a  current  of  dry  hydrogen  sulphide.  Formic  acid  distils 
(Db'bereiner). 

Another  and  better  process  consists  in  heating  to  100°  equal 
parts  of  oxalic  acid  and  glycerin.  Under  these  conditions, 
the  oxalic  acid  breaks  up  into  carbonic  acid  gas,  and  formic  acid 
which  distils.  The  liquid  is  saturated  with  lead  carbonate,  and 
the  preparation  concluded  as  before  (Berthelot). 

Properties. — Formic  acid  is  a  colorless  liquid,  having  a 
pungent  odor  and  a  very  acid  taste.  It  boils  at  99°,  and  solid- 
ities to  a  crystalline  mass  at  8.5°.  It  mixes  with  water  in  all 
proportions. 

If  an  excess  of  sulphuric  acid  be  added  to  a  small  quantity 
of  formic  acid  contained  in  a  test-tube,  and  a  gentle  heat  be 
applied,  a  regular  disengagement  of  gas  will  take  place  ;  it  may 
be  ignited  at  the  mouth  of  the  tube,  and  will  burn  with  a  blue 
flame. 

It  is  carbon  monoxide,  and  is  formed  according  to  the  fol- 
lowing equation : 

CH202  =  CO  +  H20 

If  formic  acid  be  added  to  a  solution  of  silver  nitrate,  and 
the  liquid  be  heated,  it  will  soon  become  clouded ;  silver  will 
be  precipitated  as  a  gray  powder,  and  carbon  dioxide  will  be 
disengaged. 

The  formic  acid  becomes  oxidized  in  reducing  the  silver 
nitrate, 

CH202  +  0  =  CO2  +  H20 

Chlorine  determines  an  analogous  decomposition. 
CH202  +  Cl2  ==  CO2  +  2HC1 

Formates. — Formic  acid  is  an  energetic  acid,  perfectly  neu- 
tralizing the  bases.  It  is  monobasic;  one  of  its  hydrogen 
atoms  can  be  replaced  by  an  equivalent  quantity  of  metal.  The 
formates  are  soluble ;  the  most  characteristic  are  cupric  for- 
mate, Cu(CH02)2  -f-  4H2O,  which  crystallizes  in  magnificent, 
oblique  rhombic  prisms,  and  lead  formate,  Pb(CH02/2,  which 
forms  long,  colorless  needles,  slightly  soluble  in  cold  water. 

Ammonium  formate,  which  is  obtained  by  saturating  formic 
acid  with  ammonia,  crystallizes  in  prisms  which  are  very  solu- 
ble in  water.     When  quickly  heated  to  about  200°,  it  breaks 
up  into  hydrocyanic  acid  (formonitrile)  and  water  (Pelouze). 
(NIP)CHO2  =  2H20  +  CNH 


492  ELEMENTS   OF   MODERN   CHEMISTRY. 


FORMIC  ALDEHYDE. 
CH*0  =  H-CHO 

Hofmann  has  recently  obtained  this  body  by  the  slow  com- 
bustion of  methyl  alcohol,  brought  about  by  a  spiral  of  platinum 
wire. 

CH40  +  O  =  H20  +  CH20 

It  is  also  formed  in  the  distillation  of  barium  and  calcium 
formates.  It  is  not  known  in  the  pure  state.  It  has  a  great 
tendency  to  become  polymerized,  forming  a  solid  compound, 
which  Boutlerow  has  named  trioxymethylene,  and  which  prob- 
ably contains  C3H603. 


ACETIC  COMBINATIONS. 

It  may  be  admitted  that  these  compounds  contain  the  mon- 
atomic  radical  acetyl  (C2H03/  =  (CH3-CO)',  which  may  be 
regarded  as  oxidized  ethyl. 

CH3 


Ethyl.  Acetyl. 

Aldehyde  is  the  hydride  of  this  radical  ;  acetic  acid  is  its 
hydrate,  and  acetone  its  methylide.  Besides  these,  there  are 
known  the  oxide  and  chloride  of  acetyl,  an  acetyl  ammonia, 
which  is  acetamide,  etc. 

The  following  formulae  indicate  the  relations  between  all  of 
these  bodies  : 

C2H3O.H  C2H3.OH 

Acetyl  hydride  (aldehyde).  Acetyl  hydrate  (acetic  acid). 

C2H3O.C1  (C2II30)20 

Acetyl  chloride.  Acetyl  oxide  (acetic  anhydride). 

C2H30 
C2H3O.CH3  H     N 


Acetyl  methylide  (acetone).  Acetamide. 

ACETIC   ACID. 
C2H<02 

Acetic  acid  is  the  acid  of  vinegar.  It  is  the  product  of  the 
oxidation  of  alcohol.  It  is  formed  in  a  number  of  other  reac- 
tions, among  which  we  may  mention  the  oxidation  of  aldehyde, 


ACETIC   ACID.  493 

the  decomposition  of  methyl  cyanide  by  potassium  hydrate,  the 
action  of  carbon  dioxide  on  sodium-methyl,  and  the  dry  distil- 
lation of  a  great  number  of  organic  substances,  such  as  wood, 
starch,  gum,  sugar,  etc. 

Preparation. — The  large  quantities  of  acetic  acid  employed 
in  the  arts  are  obtained  by  the  destructive  distillation  of  wood. 

The  operation  is  conducted  in  large  iron  cylinders,  heated 
directly  by  a  fire  (Fig.  123).  The  products  of  the  distillation 


consist  of  liquids  and  gases.  The  liquids  are  condensed  in  a 
large  worm,  «,  cooled  by  a  continual  circulation  of  cold  water 
through  surrounding  pipes  mm  ;  the  gases  are  conducted  back 
to  the  fire-grate  by  the  pipe  h.  The  condensed  product  consists 
of  an  aqueous  portion  and  of  tar.  The  greater  part  of  the 
latter  is  separated  by  a  new  distillation ;  the  first  portions 
which  pass  contain  wood-spirit,  after  which  acetic  acid  distils. 
The  acid  liquid  is  neutralized  by  lime,  and  the  calcium  ace- 
tate formed  is  converted  into  sodium  acetate  by  adding  a  solu- 
tion of  sodium  sulphate.  The  liquid,  separated  by  filtration 
from  the  calcium  sulphate,  yields  on  evaporation  sodium  ace- 
tate, still  colored  brown  by  tarry  matters.  The  latter  are 
destroyed  by  frying  the  salt,  that  is,  by  heating  it  for  some 
time  to  250°,  a  temperature  which  carbonizes  the  tar  but  does 
not  affect  the  sodium  acetate.  The  mass  is  then  exhausted 
with  water,  the  solution  filtered,  concentrated,  and  crystallized. 
Crystals  of  pure  sodium  acetate  are  thus  obtained,  a  salt  which 
was  formerly  called  pyrolignite  of  soda.  Acetic  acid  is  pre- 
42 


494 


ELEMENTS    OF    MODERN    CHEMISTRY. 


pared  by  drying  this  salt  and  distilling  it  with  J  its  weight  of 
concentrated  sulphuric  acid. 

Or  the  dry  salt  may  be  decomposed  by  an  exact  quantity  of 
sulphuric  acid.  The  acetic  acid  which  separates  from  the 
sodium  sulphate  may  then  be  decanted,  and  cooled  in  a  freez- 
ing mixture.  The  portion  remaining  liquid  is  separated  and 
the  solid  mass  constitutes  pure  acetic  acid. 

Vinegar. — Vinegar  is  the  product  of  the  acid  fermentation 
of  wine  and  other  alcoholic  liquids.  The  following  process  is 
largely  employed  for  the  conversion  of  wine  into  vinegar.  It 
is  the  Orleans  process.  A  small  quantity  of  warm  vinegar  is 
first  introduced  into  large  vats,  which  have  already  been  used 
for  the  operation  and  are  impregnated  with  the  peculiar  fer- 
ment formed ;  quantities  of  wine  are  then  added  at  intervals 
of  several  days,  the  vats  being  maintained  at  a  temperature 
between  24  and  27°.  In  a  fortnight,  the  acetification  is  com- 
plete, and  a  portion  of  the  vinegar  is  withdrawn  and  replaced 
by  a  new  quantity  of  wine  which  also  becomes  converted  into 
vinegar.  The  process  is  thus  continuous.  Under  these  cir- 
cumstances, the  alcohol  is  converted  into  acetic  acid  by  the 
influence  of  a  peculiar  ferment  that  is  called  mother  of  vinegar. 

It  is  a  vegetable  product, 
a  mycoderm  ( Mycoderrna 
aceti),  which  appears  on 
the  surface  of  the  liquid, 
where  it  absorbs  oxygen 
from  the  air  and  subse- 
quently cedes  it  to  the 
alcohol  (Pasteur).  Its 
action  may  be  compared 
to  that  of  platinum  black. 
By  another  process,  a 
mixture  of  weak  alcohol, 
water,  and  albuminoid 
matter  (the  juice  of  pota- 
toes, beets,  etc.),  contain- 
ing the  elements  neces- 
sary for  the  production  of 
the  ferment,  is  allowed  to 
trickle  over  beech-wood 
shavings.  The  latter,  which  have  been  previously  steeped  in 
strong  "vinegar,  are  contained  in  a  large  cask,  A  (Fig.  124), 


FIG.  124. 


ACETATES.  495 

where  they  rest  upon  a  double  bottom  perforated  with  holes. 
Tubes,  ttj  pass  through  the  upper  portion,  maintaining  a  current 
of  air  which  enters  at  the  lower  portion  of  the  cask.  Under 
these  conditions,  the  liquid,  which  spreads  over  the  shavings 
and  exposes  a  considerable  surface  to  the  air,  becomes  oxidized 
with  such  energy  that  the  temperature  soon  rises  to  30°  ;  a 
second  passage  of  the  liquid  through  the  casks  completes  the 
acetification. 

Properties  of  Acetic  Acid. — Acetic  acid  is  solid  below  1*7°, 
and  crystallizes  in  large  plates.  It  boils  at  118°.  Its  density 
at  0°  is  1.0801.  Its  odor  is  pungent  and  acid.  It  is  very 
corrosive.  It  mixes  with  water  and  alcohol  in  all  proportions, 
and  when  it  is  added  to  water  there  is  a  contraction  in  volume. 
The  maximum  contraction,  and  consequently  the  maximum 
density  of  aqueous  acetic  acid,  corresponds  to  a  mixture  con- 
taining C2H402  -f  H20. 

Vapor  of  acetic  acid  passed  through  an  incandescent  porce- 
lain tube  yields  gases  and  deposits  carbon,  at  the  same  time 
forming  small  quantities  of  acetone,  benzol,  phenol,  and  naph- 
thaline (Berthelot). 

Phosphorus  pentachloride  converts  acetic  acid  into  acetyl 
chloride,  with  formation  of  hydrochloric  acid  and  phosphorus 
oxychloride. 

C2H3O.OH  +  PCP  =  C2H3O.C1  +  HC1  +  POC13 

Acetic  acid.  Acetyl  chloride. 

If  a  mixture  of  small  quantities  of  potassium  acetate  and 
arsenious  oxide  be  heated  in  a  test-tube,  dense  white  vapors 
having  an  intense  and  disagreeable  odor  of  garlic  will  be  dis- 
engaged. 

This  experiment  permits  the  detection  of  minute  traces  of 
acetic  acid ;  if  the  latter  exist  in  the  free  state  in  the  liquid, 
its  potassium  compound  must  first  be  formed.  The  white 
vapor  disengaged  is  due  to  a  body  formerly  known  as  fuming 
liquor  of  Cadet  (see  page  453). 

ACETATES. 

The  more  important  neutral  acetates  have  the  composition 
R'(C2H302)  or  R"(C2H302)2,  according  as  the  metal  which 
replaces  the  basic  hydrogen  of  the  acetic  acid  is  univalent  or 
bivalent.  There  are  many  basic  acetates. 

Potassium  Acetate,  KC2H302.— This  is  prepared  by  satu- 


496  ELEMENTS    OF    MODERN    CHEMISTRY. 

rating  acetic  acid  with  potassium  carbonate  and  evaporating  to 
dryness.  It  is  thus  obtained  in  crystalline,  very  deliquescent 
laminae.  It  melts  at  292°,  and  is  very  soluble  in  water. 

Sodium  Acetate,  NaC2H3O2  -f  3H20.—  This  salt  is  obtained 
on  a  large  scale  in  the  arts  in  the  manufacture  of  acetic  acid. 
It  was  formerly  called  pyrolignite  of  soda.  It  crystallizes  in 
large,  oblique  rhombic  prisms,  which  are  very  soluble  in  water, 
and  effloresce  in  dry  air. 

Acetates  of  Lead.— Neutral  lead  acetate,  Pb(C2H302)2  -f 
3H20,  known  also  as  sugar  of  lead,  is  made  by  neutralizing 
acetic  acid  with  litharge.  It  crystallizes  in  transparent,  efflor- 
escent, oblique  rhombic  prisms,  having  a  sweet  and  astringent 
taste.  It  dissolves  in  half  its  weight  of  cold  water,  and  in  8 
parts  of  alcohol.  It  melts  in  its  water  of  crystallization  at 
75.5°. 

The  neutral  solution  of  lead  acetate  dissolves  oxide  of  lead, 
forming  different  basic  salts,  according  to  the  proportion  of 
oxide  dissolved.  The  more  important  of  these  are  a  dibasic 
acetate,  Pb(C2H302)2  -f  PbO  -f  4H20,  and  a  tribasic  acetate, 
Pb(C3H302)2  -f  2PbO  -f  nH20.  These  two  salts  are  gener- 
ally formed  simultaneously  when  a  solution  of  lead  acetate  is 
boiled  with  litharge.  The  solution  thus  obtained  is  used  in 
medicine  as  Goulard's  solution.  If  a  few  drops  of  it  be  added 
to  ordinary  river  or  well  water,  a  cloud  is  produced,  owing  to 
the  formation  of  lead  sulphate  and  carbonate. 

If  carbonic  acid  gas  be  passed  into  a  solution  of  the  sub- 
acetate  of  lead,  a  deposit  of  lead  carbonate  is  formed.  In  this 
reaction,  which  serves  for  the  preparation  of  white  lead  by  the 
Clichy  method,  the  excess  of  lead  is  removed  from  the  subace- 
tate  by  the  carbonic  acid,  neutral  acetate  being  formed  and 
remaining  in  solution, 

Acetates  of  Copper.— The  neutral  acetate  Cu(C2H302)2  + 
IPO,  is  prepared  by  double  decomposition  by  mixing  hot  solu- 
tions of  sodium  acetate  and  cupric  sulphate.  The  cupric  acetate 
is  deposited  on  cooling  in  beautiful,  oblique  rhombic  prisms 
of  a  deep  bluish-green  color.  They  dissolve  in  5  times  their 
weight  of  boiling  water.  The  dilute  aqueous  solution  is  de- 
composed by  boiling,  a  tribasic  acetate  being  formed,  while 
acetic  acid  is  set  free. 

When  cupric  acetate  is  heated,  it  first  loses  its  water  of  crys- 
tallization, and  decomposes  when  the  temperature  reaches  240 
or  250°,  disengaging  acetic  acid,  acetone,  and  carbon  dioxide. 


ETHYL   ACETATE.  497 

The  residue  is  finely-divided  copper.  The  product  of  the  dis- 
tillation is  a  blue  liquid,  which,  when  rectified,  yields  colorless 
acetic  acid  mixed  with  a  small  quantity  of  acetone.  It  was 
formerly  called  radical  vinegar. 

The  name  verdigris  is  applied  to  a  basic  acetate  of  copper 
consisting  mostly  of  a  dibasic  acetate,  Cu(C2H302)2  -f-  CuO  -f- 
6  IPO.  Verdigris  is  prepared  by  exposing  to  the  air  copper 
sheets  piled  up  in  layers  with  the  pulp  of  grapes.  In  a  few 
weeks  the  metal  becomes  covered  with  bluish  crusts  of  verdi- 
gris, which  are  scraped  off  and  delivered  to  commerce  in  the 
form  of  light-blue  balls.  The  alcohol,  formed  by  the  fermenta- 
tion of  the  sugar  contained  in  the  grape-pulp,  becomes  oxidized 
by  the  air  and  is  converted  into  acetic  acid,  and  under  the  in- 
fluence of  the  latter,  the  copper  itself  absorbs  oxygen.  Water 
and  copper  basic  acetate  are  thus  formed. 

Silver  Acetate,  AgC2H302.—  This  salt,  which  is  but  slightly 
soluble  in  water,  is  precipitated  when  concentrated  solutions 
of  sodium  acetate  and  silver  nitrate  are  mixed.  It  is  deposited 
from  boiling  water  in  brilliant,  pearly,  flexible  plates,  which 
darken  on  exposure  to  light. 

Ammonium  Acetate,  (NH*)C2H302.  —  When  acetic  acid  is 
saturated  by  a  current  of  ammonia  gas,  this  salt  is  obtained  as 
a  deliquescent,  crystalline  mass.  It  is  very  soluble  in  water 
and  in  alcohol.  When  heated,  it  first  loses  ammonia,  then 
acetic  acid,  and  acetamide  finally  distils. 

NH4.C2H302    =    H20     +     C2H3O.NH2 

Ammonium  acetate.  Acetamide. 

It  is  used  in  medicine  under  the  name  spirit  of  Mindererus. 
This  is  generally  an  impure  solution  of  ammonium  acetate, 
charged  with  empyreumatic  matters. 

When  distilled  with  phosphoric  anhydride,  ammonium  ace- 
tate yields  methyl  cyanide,  or  acetonitrile. 

NH*.C2H302  =  C2H3N  +  2H20 
ETHYL  ACETATE. 


This  acetate,  ordinarily  known  as  acetic  ether,  is  prepared 
by  distilling  a  mixture  of  alcohol,  sulphuric  acid,  and  potassium 
or  sodium  acetate.  The  ethyl  acetate  passes  over,  together 
with  a  certain  quantity  of  alcohol  which  escapes  the  reaction. 

42* 


498  ELEMENTS   OP   MODERN   CHEMISTRY. 

It  is  purified  by  agitation  with  a  solution  of  calcium  chloride, 
and  the  ether  which  floats  is  decanted,  dried  over  calcium 
chloride,  and  rectified  on  the  water-bath. 

It  is  a  colorless  liquid  having  a  very  agreeable,  ethereal  odor. 
It  boils  at  77°.  Density  at  0°,  0.9105.  It  is  but  slightly 
soluble  in  water,  but  dissolves  in  all  proportions  in  alcohol  and 
ether.  Like  all  compound  ethers,  it  is  readily  decomposed  by 
potassium  hydrate. 

C2H5.C2IF02  +  KOH  =  KC2IP02  +  CTP.OH 
Ammonia  converts  it  into  acetamide  and  alcohol. 
C2H3O.OC2H5  +  NH3  =  C2H5.OH  -f  C2H3O.NH2 

Ethyl  acetate  undergoes  a  remarkable  reaction  with  sodium. 
The  metal  dissolves  in  the  ether,  forming  sodium  ethylate  and 
the  compound  C6H9NaO3. 

2[C2H3O.OC2H5]  -f  Na2  =  NaO.C2H5  +  C6H9Na03  -f  H2 

The  body  C6IPNa03  is  the  sodium  compound  of  acetyl-acetic 
ether,  C6H1003  ==  C2H2(C2HWO-OC2H5,  which  is  derived 
from  acetic  ether,  C2H30-OC2H5,  by  the  substitution  of  an 
acetyl  group,  C2H30,  for  one  atom  of  hydrogen  in  the  radical 
acetyl.  The  free  acetyl-acetic  ether  may  be  obtained  by  the 
action  of  hydrochloric  acid  upon  the  sodic  compound  C6H9Na03. 
It  is  a  colorless  liquid  having  an  agreeable  odor,  and  boiling  at 
182°.  Density  at  5°,  1.03. 

SUBSTITUTION   PRODUCTS  OF  ACETIC   ACID. 

Three  chlorinated  acids  are  known  which  are  derived  from 
acetic  acid  by  substitution : 

Monochloracetic  acid C2H3C102 

Dichloracetic  acid C*H*C120» 

Trichloracotic  acid C2HC1302 

Monochloracetic  acid  is  formed  when  a  current  of  chlorine 
is  passed  into  acetic  acid  heated  to  100°,  and  containing  a  small 
quantity  of  iodine.  As  soon  as  chlorine  begins  to  be  disen- 
gaged at  the  extremity  of  the  apparatus,  the  operation  is  arrested 
and  the  liquid  distilled.  That  portion  is  collected  which  passes 
between  185  and  187°. 

Monochloracetic  acid  is  solid,  and  crystallizes  in  deliquescent, 
rhomboidal  tables  or  in  prisms.  It  boils  between  185  and  187.8°. 


ACETIC   ANHYDRIDE.  499 

It  is  very  corrosive.     It  is  converted  into  glycollic  acid  when 
heated  with  an  excess  of  potassium  hydrate. 
KC2H2C102     +     KOH    =    KC2H2(OH)02     +     KC1 

Potassium  Potassium  glycollate. 

monochloracetate. 

Ammonia  converts  it  into  acetamic  or  amidacetic  acid  C2H2 
(NH2)O.OH  (glycocol)  (Cahours). 


+     NH3     -     HCl     + 
CO.OH  CO.OH 

Monochloracetic  acid.  Glycocol. 

Trichloracetic  acid,  C2HC1302,  a  very  important  compound 
in  the  history  of  the  science,  was  discovered  by  Dumas  in  1840. 
It  was  then  one  of  the  most  remarkable  examples  of  a  body 
formed  by  substitution,  and  a  comparison  of  its  properties  with 
those  of  acetic  acid  led  Dumas  to  announce  the  first  idea  of 
chemical  types. 

It  is  obtained  by  exposing  acetic  acid  to  the  action  of  a  large 
excess  of  chlorine  in  direct  sunlight. 

Trichloracetic  acid  is  solid.  It  forms  transparent  and  deli- 
quescent, rhombohedral  crystals,  fusible  at  52.3°,  and  boiling 
between  195  and  200°. 

Its  aqueous  solution  regenerates  acetic  acid  by  the  action  of 
sodium  amalgam,  an  interesting  reaction,  since  it  furnished  one 
of  the  first  examples  of  inverse  substitution  (Melsens),  as  the 
replacement  of  chlorine  by  hydrogen  is  called.  Water  and 
sodium  amalgam  constitute  a  slow  source  of  hydrogen. 

When  boiled  with  potassium  hydrate,  trichloracetic  acid  fur- 
nishes potassium  carbonate  and  chloroform. 
C2HCP02  =  CHC13  +  CO2 

ACETIC  ANHYDRIDE. 


This  important  body,  discovered  by  Gerhardt  in  1852,  is 
prepared  by  the  action  of  one  part  of  phosphorus  oxychloride 
on  three  parts  of  dry  sodium  acetate.  In  this  operation,  acetyl 
chloride  is  first  formed,  and  this  reacts  upon  an  excess  of  so- 
dium acetate,  producing  sodium  chloride  and  acetyl  acetate,  or 
acetic  anhydride. 


CTPO.C1  +         NO   =   NaCl  + 

Acetyl  chloride.         Sodium  acetate.  Acetic  anhydride. 


500  ELEMENTS    OF    MODERN    CHEMISTRY. 

Acetic  anhydride  is  a  colorless,  mobile  liquid,  having  a  strong 
odor  of  acetic  acid.  It  boils  at  138°.  When  thrown  into 
water,  it  first  sinks  to  the  bottom,  and  then,  absorbing  one  mol- 
ecule of  water,  is  converted  into  acetic  acid,  which  dissolves. 

ALDEHYDE,  OK  HYDRIDE   OF  ACETYL. 
C2H*O 

This  body  was  discovered  by  Dbbereiner  in  1821 ;  its  com- 
position and  principal  properties  were  studied  by  Liebig. 

Preparation. — Aldehyde  is  prepared  by  oxidizing  alcohol  by 
heating  it  with  manganese  dioxide  and  dilute  sulphuric  acid, 
or  better,  with  potassium  dichromate  and  sulphuric  acid.  The 
vapors  disengaged  are  condensed  in  a  well-cooled  receiver.  The 
distilled  liquid  is  rectified  over  calcium  chloride,  only  the  more 
volatile  portion  being  collected.  This  is  mixed  with  twice 
its  volume  of  ether,  and  the  ethereal  solution  saturated  with 
ammonia  gas.  Crystals  are  deposited  which  constitute  a  com- 
bination of  aldehyde  with  ammonia,  and  the  aldehyde  is  ob- 
tained from  them  by  adding  a  quantity  of  sulphuric  acid  exactly 
sufficient  to  form  ammonium  sulphate  with  the  ammonia;  a 
gentle  heat  is  applied,  and  the  aldehyde  vapor  is  passed  through 
a  tube  filled  with  calcium  chloride,  and  finally  condensed  in  a 
well-cooled  receiver  (Liebig). 

Properties. — Aldehyde  is  a  colorless,  very  mobile  liquid, 
having  a  penetrating  and  somewhat  suffocating  odor.  It  boils 
at  21°.  It  mixes  in  all  proportions  with  water,  alcohol,  and 
ether. 

It  combines  with  ammonia,  forming  aldehyde-ammonia,  or 
acetylide  of  ammonium  (Liebig). 

C2H4O.NH3  =  C2H3O.NH4 

It  unites  with  the  alkaline  acid-sulphites,  forming  crystal- 
lizable  combinations. 

It  is  very  apt  to  become  oxidized,  being  transformed  into 
acetic  acid. 

C2H40  +  0  =  C2H402 

If  some  aldehyde  and  a  few  drops  of  ammonia  be  added  to 
a  solution  of  silver  nitrate,  and  a  gentle  heat  be  applied,  the 
liquid  soon  becomes  clouded,  and  the  sides  of  the  vessel  con- 
taining it  are  covered  with  a  brilliant  deposit  of  metallic  silver. 


ALDEHYDE.  501 

By  the  action  of  sodium  amalgam  and  water,  aldehyde  fixes 
two  atoms  of  hydrogen,  and  is  converted  into  alcohol  (A. 
Wurtz). 

C2H40  +  H2  =  C2H60 

When  hydrochloric  gas  is  passed  into  a  mixture  of  aldehyde 
and  absolute  alcohol,  monochlorether  is  formed. 


C2H*0  +  C2H5.0H  +  HC1  =  IPO 

Monochlorether. 

Chlorine  converts  aldehyde  into  acetyl  chloride  and  other 
products  (A.  Wurtz). 

C2H3O.H  +  CP  ==  C2H3O.C1  +  HC1 

When  treated  with  phosphorus  pentachloride,  aldehyde  ex- 
changes its  atom  of  oxygen  for  two  atoms  of  chlorine,  and  is 
transformed  into  monochlorethyl  chloride,  C2H4C12  (ethylidene 
chloride). 

CH3  CH3 

PC1!  ^    inc.. 


Aldehyde.  Ethj  Hdene  chloride. 

Aldehyde  has  a  great  tendency  to  become  converted  into 
polymeric  modifications.  Among  these  are  paraldekyde,  which 
is  liquid,  and  metaldehyde,  which  is  solid  (Liebig). 

Dry  hydrochloric  acid  gas  converts  aldehyde  into  ethylidene 
oxy  chloride  (an  isomeride  of  dichlorether),  eliminating  water. 

2C2H4O  +  2HC1    =    C4H8C120     +     H20 

Ethylidene  oxychloride. 

By  the  action  of  hydrochloric  acid  diluted  with  twice  its 
volume  of  water,  aldehyde  doubles  its  molecule  and  is  converted 
into  a  thick,  colorless,  neutral  body,  boiling  at  95°  in  a  vacuum  ; 
it  is  soluble  in  water  and  reduces  ammoniacal  silver  nitrate. 
This  body  is  aldol,  C4H8O2  (A.  Wurtz). 

When  heated  with  ordinary  hydrochloric  acid,  aldehyde  gives 
crotonic  aldehyde  (Kekule). 

2C2H4O     =     H20     +     C4H60 

Aldehyde.  Crotonic  aldehyde. 

The  same  transformation  takes  place  when  aldehyde  is  heated 
to  100°  with  a  small  quantity  of  zinc  chloride  and  a  trace  of 
water. 


502  ELEMENTS   OF    MODERN   CHEMISTRY. 

ACETYL  CHLORIDE. 


COC1 

This  body  was  obtained  by  Gerhardt  in  1852,  by  treating 
sodium  acetate  with  pentachloride,  or  oxychloride  of  phos- 
phorus. 

NaC2H302  -f-  PCI5  ==  C2H3OC1  +  NaCl  -f  POCP 

Sodium  acetate.  Acetyl  chloride.  Phosphorus  oxychloride. 

It  is  also  formed  by  the  action  of  chlorine  on  aldehyde. 

It  is  a  colorless,  mobile  liquid,  having  a  pungent  odor.  It 
boils  at  55°. 

If  it  be  poured  into  water,  it  sinks  to  the  bottom,  but  rapidly 
decomposes  into  hydrochloric  and  acetic  acids. 

C2H3O.C1  +  H20  =  HC1  -f  C2H3O.OH 

It  undergoes  a  similar  decomposition  with  alcohol,  forming 
ethyl  acetate  and  hydrochloric  acid. 

C2H3O.C1  -f  C2H5.OH  =  HC1  -f  C2H5.C2H302 
With  ammonia,  it  forms  acetamide  and  ammonium  chloride. 

C2H3O.C1  +  2NH3  ==  NH4C1  +  C2H3O.NH2 
It  reacts  with  acetates,  forming  acetic  anhydride. 

TRICHLORACETYL  HYDRIDE,  OR  TRICHLORAL- 
DEHYDE. 

(CHLORAL.) 


This  important  body  was  discovered  by  Liebig  and  Dumas. 
It  is  formed  by  the  prolonged  action  of  chlorine  on  alcohol. 
It  is  a  colorless,  mobile  liquid,  having  a  peculiar,  penetrating 
odor.  It  boils  at  94.4°  (Dumas). 

Gerhardt  regarded  it  as  aldehyde  in  which  the  three  atoms 
of  hydrogen  of  the  radical  are  replaced  by  three  atoms  of 
chlorine. 

C2H3O.H  C2C13O.H 

Aldehyde.  Chloral. 

(Acetyl  hydride.)  (Trichloracetyl  hydride.) 

Its  reactions  resemble  those  of  aldehyde.  It  forms  crystal- 
lizable  compounds  with  the  disulphites.  Its  ammoniacal  solu- 


ACETONE.  503 

tion  reduces  silver  nitrate.  These  facts  seem  to  indicate  that 
chloral  contains  the  group  CHO,  which  is  characteristic  of  the 
aldehydes  ;  its  constitution  is  then  expressed  by  the  formula 

CCP 

CHO 

It  regenerates  aldehyde  by  the  action  of  nascent  hydrogen 
(Personne). 

The  alkaline  hydrates  decompose  it  into  chloroform  and  a 
formate  (Dumas). 

C2HCPO  -f  KOH  =  ECHO2  +  CHOP. 

Chloral.  Potassium  formate. 

Nitric  acid  converts  it  into  trichloracetic  acid,  in  the  same 
manner  that  aldehyde  is  converted  into  acetic  acid. 

C2HCPO  -f  0  =  C2HCP02 

Chloral  forms  a  crystallizable  compound  with  water,  C2HCPO 

CCP 
+  H20  =    l  »  called    chloral    hydrate.      The   latter 

melts  at  57°,  and  boils  at  98°  (Personne),  being  at  the  same 
time  decomposed  into  anhydrous  chloral  and  water.  It  is  very 
soluble  in  water. 

In  contact  with  concentrated  sulphuric  acid,  chloral  is 
rapidly  converted  into  a  white,  solid  substance  which  is  insol- 
uble in  water  ;  it  has  the  same  composition  as  ordinary  chloral, 
and  is  called  insoluble  chloral. 

Chloral  also  combines  with  alcohol,  forming  alcoholate  of 
chloral  (Personne). 

Chloral  hydrate  has  for  some  time  been  successfully  employed 
in  medicine  as  an  anodyne  and  hypnotic. 

ACETONE. 


Acetone  is  the  methylide  of  acetyl,  C2H3O.CH3,  and  since 
acetyl  itself  is  carbonyl  (carbon  monoxide)  methylide,  CH3-CO, 
acetone  can  be  regarded  as  carbonyl  dimethylide,  CH3-CO-CH3. 


"  I 
1 


CI  ro"  I  CH3 

Cl  i  CH» 


Carbonyl  chloride.  Carbonyl  dimethylide  (acetone). 

Indeed,  the  synthesis  of  acetone  has  been  made  both  by  treat- 


504  ELEMENTS    OF    MODERN    CHEMISTRY. 

ing  acetyl  chloride  with  zinc  methyl  (Pebal  and  Freund),  and 
by  treating  sodium  methyl  with  chlorocarbonic  gas  (carbonyl 
chloride). 

Zn(CH3)2  -f  2(C2H3O.C1)  =  2(C2H3O.CH3)  +  ZnCl2 

Zinc  methyl.  Acetyl  chloride.  Acetone. 

2(CH3.Na)  -f  CO  j  ^}  =  2NaCl  +  CO 

Sodium  methyl.        Carbonyl  chloride.  Acetone. 

Preparation. — Acetone  is  prepared  by  distilling  dry  calcium 
acetate  in  a  clay  retort.  The  vapors  given  off  are  condensed 
in  a  well-cooled  receiver,  and  the  liquid  obtained  is  distilled  on 
a  water-bath  with  an  excess  of  calcium  chloride. 

Ca(C2H302)2  =  C3H60  -f  CaCO3 

Properties. — Acetone  is  a  colorless  liquid,  having  a  slightly 
empyreumatic,  ethereal  odor.  It  boils  at  56°.  It  dissolves  in 
all  proportions  in  water,  alcohol,  ether,  and  wood-spirit. 

Like  aldehyde,  it  forms  crystallizable  combinations  with  the 
alkaline  acid-sulphites. 

In  presence  of  nascent  hydrogen,  produced  by  sodium  amal- 
gam and  water,  it  fixes  H2  and  is  converted  into  isopropyl 
alcohol  (Friedel). 

CH3  CH3 

CO    -f     H2    =    CH.OH 

CH3  CH3 

Acetone.  Isopropyl  alcohol. 

It  is  seen  by  this  method  of  formation  that  isopropyl  alcohol 
contains  a  group  CHOH,  united  to  two  methyl  groups ;  it  is  a 
secondary  alcohol  (page  473). 

Isopropyl  alcohol  is  not  the  only  product  of  the  action  of 
nascent  hydrogen  on  acetone.  The  reaction  gives  rise  to  a 
product  of  condensation  resulting  from  the  addition  of  H2  to 
two  molecules  of  acetone.  This  has  received  the  name  pina- 
cone. 

2C3H60  +  H2  =  C6HW02 

Pinacone. 

It  is  a  tertiary  glycol  (see  page  522).  It  constitutes  a  color- 
less, crystallizable  mass,  fusible  between  35  and  38°,  and  boil- 
ing at  171-172°.  By  the  action  of  dilute  and  hot  sulphuric 
or  hydrochloric  acid,  it  loses  one  molecule  of  water  and  is  con- 


ACETAMIDE.  505 

verted  into  a  neutral  liquid,  boiling  at  106°.     This  is  pinaco- 
lin,  C6H120. 

When  acetone  is  added  in  small  portions  to  phosphorus 
pentachloride,  a  very  energetic  reaction  takes  place  and  two 
chlorides  are  formed.  One  of  them,  C3H6C12  (methylchlor- 
acetol),  boils  at  70°.  The  other,  C3H5C1  (monochloropropy- 
lene),  boils  at  23°  (Friedel). 

C3H60  +  PCI5  =  C3H6C12  +  POC13 
C3H6CP  =  C3H5C1  +  HC1 

Hot,  concentrated  sulphuric  acid  removes  the  elements  of 
water  from  acetone  and  converts  it  into  a  hydrocarbon,  which 
has  received  the  name  mesitylene  (Kane). 

3C3H60  —  3H20  =  C9H12 

Acetone.  Mesitylene. 

ACETAMIDE. 

C2H3O.NH2 

This  amide  may  be  obtained  by  heating  ethyl  acetate  to  100° 
in  sealed  tubes  with  aqueous  ammonia.  Alcohol  and  acetamide 
are  formed  according  to  the  equation 

C2H5.C2H302  +  NH3  =  C2H3O.NH2  +  C2H5.OH 

When  the  resulting  liquid  is  evaporated  in  a  vacuum,  the 
acetamide  remains.  It  may  be  purified  by  distillation,  collecting 
that  which  passes  above  200°. 

Acetamide  is  also  formed  by  the  action  of  ammonia  on  acetyl 
chloride ;  one  of  the  readiest  methods  of  preparing  it  consists 
in  simply  distilling  ammonium  acetate. 

It  is  a  solid,  crystallizable  body,  soluble  in  water  in  all  pro- 
portions. Its  odor  resembles  that  of  mice.  Boiling  potassium 
hydrate  reacts  with  it,  forming  potassium  acetate  and  ammonia. 
Phosphoric  anhydride  removes  from  it  the  elements  of  water, 
converting  it  into  acetonitrile  or  methyl  cyanide. 
C2H3O.NH2  =  C2H3N  +  H2O 

ACIDS   OF   THE  SERIES  CnH2n02 

Formic  and  acetic  acids,  of  which  the  principal  compounds 

have  just  been  described,  are  the  first  terms  of  a  very  extensive 

homologous  series.     It  is  the  series  of  volatile  fatty  acids,  so 

named  because  it  includes  a  great  number  of  compounds  which 

w  43 


506 


ELEMENTS    OF    MODERN    CHEMISTRY. 


were  at  first  obtained  from  the  natural  fatty  bodies,  and  which 
are  the  fatty  acids  proper.  Among  the  bodies  congeneric  with 
acetic  acid,  those  of  which  the  molecules  are  less  complicated 
are  liquid  at  ordinary  temperatures  ;  the  others  are  solid.  The 
following  table  gives  the  nomenclature,  composition,  and  prin- 
cipal physical  properties  of  these  acids : 


CRUDE 
FOKMULJS. 

CH202 
C2H*02 
C3H602 
OH802 

C5H10Q2 

C6H1202 
C7HU02 
C8H1602 

C9H1802 


RATIONAL 
FORMULAE. 

H-CO.OH 

CH3-CO.OH 

CW-CO.OH 

C3H*-CO.OH 

C4H9-CO.OH 


MELTING- 
POINTS. 

1° 
17° 
—21° 

0° 


CW-CO.OH 


5° 


14 


C8H17-CO.OH 


BOILING- 
POINTS. 

99° 
118° 

140.7° 

163° 

175° 

199.7° 

212° 

236° 

260° 


C12H2*02 


C16H3202 
C17H3*02 
C18H36Q2 
C20H^02 
C22H4402 
C27H5402 


CWMXXOH 

27.2° 

c^ii^-co.oH 

43.6° 

C13H27-CXXOH 

53.8° 

C15H31-CO.OH 

62° 

C16H:«-CO.OH 

60° 

C17H35-CO.OH 

69.2° 

C19H39-CO.OH 

75° 

C^H^-CO.OH 

96° 

C26H53_CO.OH 

78° 

C29H59_CO.OH 

88° 

NAMES  OF   ACIDS. 

Formic  acid      .... 

Acetic  acid 

Propionic  acid  .  .  . 
Butyric  acid  .... 
Valeric  acid  (isovaleric) 
Caproic  acid  (isocaproic) 
CEnanthylic  acid  .  .  . 
Caprylic  acid  .... 
Pelargonic  acid  .  .  . 

Capric  acid 

Laurie  acid 

Myristic  acid  .... 
Palmitic  acid  .... 
Margaric  acid  .... 

Stearic  acid 

Arachnic  acid  .... 

Benic  acid 

Cerotic  acid  .... 
Melissic  acid  .... 

We  have  already  noticed  the  existence  of  numerous  isomeric 
alcohols,  and  in  their  study  the  principles  of  isomerism  have 
been  explained.  Such  isomerides  exist  also  in  the  series  of 
acids,  and  are  caused  by  the  different  atomic  structure  of  the 
radicals,  CnH2n+1,  which  figure  in  the  preceding  formulse.  We 
will  consider  two  examples.  1.  When  normal  butyl  alcohol, 
CH3-CH2-CH2-CH2.OH,  is  oxidized,  normal  butyric  acid,  or 
the  butyric  acid  of  fermentation,  is  obtained,  CH3-CH2-CH2- 
CO.OH.  The  acid  obtained  by  oxidation  of  the  butyl  alcohol 
of  fermentation  is  different  from  this,  and  the  difference  is 
caused  by  the  difference  in  structure  of  the  radicals  (C3H7)'. 

Isobutyric  acid,  derived  from  the  alcohol  of  fermentation, 

whose  constitution  is   pTT3^>CH-CH2.OH,   contains    pr™^ 

CH-CO.OH. 

The  acid  is  derived  from  the  alcohol  by  the  substitution  of 
0  for  H2  in  the  group  (CH2.OH)'. 

2.  As  we  have  already  seen,  the  constitution  of  amyl  alcohol 
of  fermentation  is  expressed  by  the  formula 


PROPIONIC   ACID.  507 

™33>CH-CH2-CH2.OH. 

The  valeric  acid  produced  by  its  oxidation  is  then 


But  normal  valeric  acid  is  also  known,  and  contains 

CH3-CH2-CH2-CH2-CO.OH 
It  results  from  the  oxidation  of  normal  amyl  alcohol 

CH3-CH2-CH2-CH2-CH2.OH 

Another  interesting  isomeride  of  valeric  acid  is  trimethyl- 
acetic  acid,  which  was  discovered  by  Boutlerow. 

If  we  compare  the  three  isomeric  acids,  C5H1002,  with  acetic 
acid  itself,  we  will  find  that  their  isomeric  relations  can  be  ex- 
pressed in  a  very  simple  manner,  by  saying  that  normal  valeric 
acid  is  propylacetic  acid,  the  acid  derived  from  the  alcohol  of 
fermentation  is  isopropylacetic  acid,  and  lastly,  that  Boutlerow's 
acid  is  trimethylacetic  acid. 


CH3  CH2(C3H7)  CH2(CH<£  C(CH3)3 

CO.OH  CO  OH  CO.OH  CO.OH 

Acetic  acid.      Propylacetic  acid.         Isopropylacetic  acid.    Trimethylacetic  acid. 

We  cannot  dwell  further  on  the  subject;  that  which  pre- 
cedes is  sufficient  to  elucidate  the  isomerism  of  acids  of  the 
series  CnH2n02. 

Propionic  Acid,  C3H602.  —  This  acid  is  formed  by  the  action 
of  potassium  hydrate  on  ethyl  cyanide.  It  is  also  a  product  of 
fermentation  ;  thus,  it  has  been  obtained  by  allowing  a  solution 
of  sugar,  mixed  with  chalk  and  cheese,  to  ferment  during  a 
year.  It  is  also  formed  in  small  quantity  in  the  distillation  of 
wood. 

Wanklyn  made  its  synthesis  by  passing  carbon  dioxide  over 
sodium  ethyl. 

CO.O     -f     C2H5Na    =     C2H5-CO.ONa 

Sodium  propionate. 

Propionic  acid  may  also  be  formed,  though  with  difficulty, 
by  the  direct  combination  of  carbon  monoxide  and  ethylate  of 
sodium. 

CO       C2H5.ONa  =  C2H5-CO.ONa 


508  ELEMENTS   OF   MODERN   CHEMISTRY. 

Properties.  —  It  is  a  colorless,  mobile  liquid,  having  an  odor 
like  that  of  acetic  acid.  It  solidifies  at  —  21°,  and  boils  at 
140.7°.  Density  at  21°,  0.996.  It  is  miscible  with  water  in 
all  proportions.  Calcium  chloride  separates  it  from  its  aqueous 
solution. 

There  are  a  great  number  of  substitution  products  directly 
related  to  propionic  acid.  Among  these  are  the  chlorine,  bro- 
mine, and  iodine  derivatives,  and  the  amides.  Two  of  these 
derivatives  are  known  of  each  particular  species,  presenting 
curious  isomeric  relations.  The  following  examples  will  serve 
as  illustrations  : 

CR3  CH3  CH2C1  CH3  CH2(NH2) 

CH2  CHC1  CH2  CH(NH2)  CH2 

C02H  C02H  C02H  C02H  <J02H 

Propionic       o-C'liloropro-     j8-Chloropro-  o-Amidopropi-      /3-Amidopropi- 

acid.  pionic  acid.        piunic  acid.  onic  ucid.  onic  acid. 

Only  the  iodo-derivatives  will  be  described  here,  and  farther 
on  we  will  mention  the  amides. 

a-iodopropiotiic  acid,  C3H3I02,  is  prepared  by  the  action  of 
concentrated  hydriodic  acid  or  phosphorus  iodide  on  lactic 
acid. 

C3H603  -f  HI  =  C3H5I02  4  H20 

Lactic  acid. 

It  is  a  thick,  oily  body,  almost  insoluble  in  water. 

ft-iodopropionic  acid  is  formed  by  the  action  of  concentrated 
hydriodic  acid  or  phosphorus  iodide  and  water  on  glyceric 
acid. 


_|_  3HI  =  C3H5I02  -f  2H20 

Glyceric  acid. 

It  is  also  formed  by  the  direct  combination  of  hydriodic  acid 
and  acrylic  acid,  C3H*02. 

It  is  a  solid,  occurring  in  crystalline  laminae,  fusible  at  82°. 
It  is  very  soluble  in  boiling  water.     When  heated  to  180° 
with  hydriodic  acid,  it  is  converted  into  propionic  acid. 
G3H5I02  +  HI  =  P  +  C3H602 

Normal  Butyric  Acid,  C*H802.  —  This  acid  was  discovered 
by  Chevreul  in  butter,  where  it  exists  in  combination  with 
glycerin  in  butyrin.  Pelouze  and  Grelis  have  shown  that  it 
is  formed  in  abundance  when  a  solution  of  sugar,  glucose,  or 
even  starch  is  abandoned  for  several  weeks  with  the  addition 


BUTYRIC    ACIDS.  509 

of  chalk  and  old  cheese.  In  about  ten  days  a  mass  of  calcium 
lactate  is  formed,  but  this  soon  disappears,  gases  being  at  the 
same  time  disengaged.  The  mass  again  becomes  liquid,  and 
the  solution  contains  calcium  butyrate.  This  is  converted  into 
sodium  butyrate,  which  is  finally  decomposed  by  sulphuric 
acid ;  the  butyric  acid  separates  in  the  form  of  an  oily  liquid, 
which  is  decanted  and  distilled. 

Properties. — Butyric  acid  is  a  colorless  liquid,  having  a 
pungent  and  disagreeable  odor  which  recalls  that  of  rancid 
butter.  It  is  quite  soluble  in  water.  Density  at  14°,  0.958. 
Boiling-point,  163°. 

It  perfectly  neutralizes  the  bases,  forming  butyrates.  These 
salts,  which  are  mostly  soluble  in  water,  have  a  fatty  aspect. 
Calcium  butyrate,  Ca(OH702),2  is  more  soluble  in  cold  water 
than  in  hot  water,  so  that  its  cold  saturated  solution  becomes 
a  solid  mass  when  heated  to  70°. 

Butyrone. — When  calcium  butyrate  is  subjected  to  dry  dis- 
tillation, it  yields,  as  principal  product,  butyrone,  one  of  the 
homologues  of  acetone  (Chancel). 

Ca(C'H702)2     =     C7H140     +     CaCO3 

Calcium  butyrate.  Butyrone. 

Butyrone  is  a  colorless  liquid,  lighter  than  water,  and  having 
a  peculiar,  ethereal  odor.  It  boils  at  144°. 

Butyral. — The  principal  product  of  the  distillation  of  a  mix- 
ture of  butyrate  and  formate  of  calcium  is  butyral,  or  butyric 
aldehyde,  C4H80. 

Ca(C4H702)2  +  Ca(CH02)2  =  2CaC03  +  2C4H80 

This  important  reaction,  discovered  by  Piria,  permits  of  the 
conversion  of  butyric  acid  into  its  aldehyde ;  it  can  also  be  ap- 
plied to  the  transformation  of  other  acids  into  aldehydes. 

Butyral,  which  was  discovered  by  Chancel,  is  a  liquid,  boil- 
ing at  about  70°.  Like  aldehyde,  it  forms  a  crystallizable 
compound  with  ammonia,  and  it  unites  with  the  alkaline  acid- 
sulphites  as  do  the  other  aldehydes  and  the  acetones. 

Isobutyric  Acid. — An  acid  isomeric  with  butyric  acid  is 
known,  and  is  designated  as  isobutyric  acid  (Morkownikof ). 

It  is  formed  by  the  oxidation  of  butyl  alcohol  of  fermenta- 
tion, and  exists  naturally  in  the  fruit  of  the  Ceratonia  siliqua 
(carob  locust,  St.  John's  bread).  It  is  also  obtained  by  decom- 
posing isopropyl  cyanide  with  potassium  hydrate. 

(C'H'/CN  4-  2H20  =  NH3  +  (C3H7)!-C02H 
43* 


510  ELEMENTS   OF   MODERN   CHEMISTRY. 

It  is  a  liquid  having  a  disagreeable  odor,  like  that  of  the 
acid  of  fermentation.  Density  at  20°,  0.9503.  It  boils  at 
154°. 

Valeric  Acid,  C5H1002. — This  acid  was  discovered  by  Chev- 
reul,  who  first  obtained  it  from  dolphin  oil  (phocenic  acid.)  It 
may  be  prepared  by  distillation  of  valerian  root  with  water ; 
hence  its  name.  It  exists  also  in  the  root  of  angelica,  in  the 
Athamanta  oreosclinum  and  in  the  fruit  and  bark  of  the  Vibur- 
num opulus.  The  same  acid  is  formed  when  amyl  alcohol  is 
oxidized  by  a  mixture  of  potassium  dichromate  and  sulphuric 
acid. 

C5H120  +  O2  =  H2O  +  C5H1002 

It  is  also  formed  when  potassium  hydrate  is  boiled  with  iso- 
butyl  cyanide,  by  a  reaction  similar  to  that  which  has  already 
been  indicated  for  the  formation  of  isobutyric  acid. 

Valeric  acid  is  a  colorless  liquid,  having  a  pungent,  disagree- 
able odor.  Density  at  0°,  0.947.  It  boils  at  175°.  It  dissolves 
in  30  parts  of  water,  from  which  it  is  precipitated  by  the  addi- 
tion of  neutral  salts.  Its  ammonium  salt  is  used  in  medicine. 

Normal  valeric  acid,  which  has  already  been  mentioned  (page 
507),  is  a  colorless  liquid,  smelling  like  butyric  acid.  It  boils 
at  184-185°,  and  its  density  at  0°  is  0.9577. 

Trimethylacetic  acid  is  formed  when  potassium  hydrate  is 
boiled  with  the  cyanide  derived  from  trimethylcarbinol. 

(CH3)3C-CN  +  2H20  =  (CH3)3C-CO.OH  +  NH3 

It  is  a  crystalline  mass,  fusible  at  35°,  and  boiling  at  163.8°. 
It  dissolves  in  40  parts  of  water  at  20°. 

Caproic  Acids. — There  are  several  isomeric  acids  having  the 
composition  C6H1202.  One  of  them  was  discovered  in  butter 
by  Chevreul.  Normal  caproic  acid  is  formed  by  the  oxidation 
of  normal  hexyl  alcohol,  and  in  the  decomposition  of  normal 
amyl  cyanide  by  boiling  potassium  hydrate.  It  is  an  oily  liquid, 
having  but  a  faint  odor ;  its  density  at  0°  is  0.945,  and  it  boils 
at  205°.  Leucine,  C6H13N02,  an  important  nitrogenized  body 
which  exists  in  the  animal  economy,  is  an  amide,  C6Hn(NH2)02, 
of  normal  caproic  acid. 

The  caproic  acid  mentioned  on  page  506  is  an  isomeride  of 
the  preceding  acid.  It  is  obtained  by  decomposing,  by  potas- 
sium hydrate,  amyl  cyanide  derived  from  the  alcohol  of  fer- 
mentation. 


FATTY   ACIDS.  511 

Our  limited  space  will  not  permit  of  a  description  of  all  of 
the  acids  of  this  series ;  we  can  only  briefly  consider  the  last 
members. 

Palmitic  Acid,  C16H3202. — This  exists  in  palm-oil  in  com- 
bination with  glycerin.  It  is  prepared  on  a  large  scale  in 
England  by  distilling  palm-oil  by  means  of  superheated  steam, 
which  decomposes  the  oil  into  fatty  acid  and  glycerin.  The 
fatty  acids  solidify  on  cooling.  The  mass  is  expressed  to  re- 
move the  liquid  oleic  acid  with  which  it  is  impregnated,  and  so 
obtained  in  dry,  white  cakes,  which  are  used  for  the  manufac- 
ture of  candles. 

Margaric  Acid,  C17H3402. — According  to  Chevreul.  this  acid 
exists  in  all  solid  fats.  To  separate  it  from  stearic  acid,  which 
always  accompanies  it,  Chevreul  recommends  the  following 
process :  olive-oil  is  saponified  with  litharge  and  water,  and  the 
lead-plaster  or  soap  thus  obtained  is  allowed  to  cool;  after 
separating  it  from  the  water  which  holds  the  glycerin  in  solu- 
tion, it  is  pulverized  and  exhausted  with  ether,  which  dissolves 
the  lead  oleate  and  leaves  the  margarate.  The  two  salts  being 
composed  by  hydrochloric  acid,  furnish  respectively  oleic  and 
margaric  acids. 

Margaric  acid  crystallizes  in  white  scales,  fusible  at  60°. 
Heintz  considers  that  the  margaric  acid  obtained  from  many 
fats  is  a  mixture  of  palmitic  and  stearic  acids. 

Stearic  Acid,  C^H^O2,  was  obtained  from  tallow  by  Chev- 
reul. It  is  a  solid,  melting  at  69.2°.  After  cooling,  the  fused 
acid  becomes  a  laminated,  white  mass.  It  is  insoluble  in 
water,  but  dissolves  in  alcohol  and  ether.  The  alcoholic  solu- 
tion deposits  it  in  small  pearly  scales,  which  are  not  greasy  to 
the  touch.  Stearic  acid  is  used  for  the  manufacture  of  stearin 
candles. 

The  alkaline  stearates  are  soluble  in  water.  If  a  large  excess 
of  water  be  added  to  the  solution  of  a  neutral  stearate,  a  crystal- 
line precipitate  is  formed  which,  according  to  Chevreul,  is  an 
acid  stearate.  On  this  reaction  he  has  founded  a  method  for 
the  preparation  of  stearic  acid. 

The  stearates  of  calcium,  barium,  and  lead  are  insoluble  in 
water,  and  can  be  obtained  by  double  decomposition. 

Cerotic  and  Melissic  Acids. — These  acids  have  been  ob- 
tained from  wax  by  Brodie  (page  480). 


512  ELEMENTS   OP   MODERN   CHEMISTRY. 


OLEIC  ACID  AND  ITS  HOMOLOGUES. 

Oleic  acid,  which  has  just  been  mentioned  and  which  Chev- 
reul  obtained  from  olein,  is  the  principal  constituent  of  a  great 
number  of  oils  and  fats ;  it  does  not  belong  to  the  series  of 
volatile  fatty  acids.  Its  formula,  C18H3402,  shows  that  it  differs 
from  stearic  acid  by  containing  two  atoms  of  hydrogen  less 
than  the  latter  acid.  It  belongs  to  the  series  CnH2n~202. 

Pure  oleic  acid  is  an  oily  liquid  which  solidified  to  a  crys- 
talline mass  at  4°.  Its  alcoholic  solution  deposits  it,  when 
cooled,  in  small  needles,  fusible  at  14°.  The  peroxide  of  nitro- 
gen converts  oleic  acid  into  a  solid,  crystallizable,  isomeric  modi- 
fication of  the  same  acid,  named  by  Brodie  elaidic  acid. 

Acrylic  Acid,  C3H402. — This  is  the  first  term  of  the  series 
CnH2n"202.  It  receives  its  name  from  the  fact  that  it  results 
from  the  oxidation  of  acrolein,  or  acrylic  aldehyde,  C3H40, 
which  is  formed  in  the  destructive  distillation  of  neutral  fatty 
substances  and  glycerin  and  its  compounds ;  it  is  a  product  of 
the  dehydration  of  glycerin. 

C3H803    ==     C3H40     +     2H20 

Glycerin.  Acrolein. 

Acrolein  reduces  silver  oxide,  like  the  other  aldehydes, 
being  converted  into  acrylic  acid.  This  acid  is  liquid,  and  boils 
above  100°.  Nascent  hydrogen  converts  it  into  propionic  acid. 

C3H402  +  H2  =  C3H602 

Crotonic  Aldehyde  and  Acid. — These  two  bodies  are  homo- 
logues  of  acrylic  aldehyde  and  acid. 

C3H40  acrylic  aldehyde.  C3H*02  acrylic  acid. 

C4H60  crotonic  aldehyde.  C4H602  crotonic  acid. 

Crotonic  aldehyde  is  one  of  the  numerous  transformation 
products  of  ordinary  aldehyde.  When  the  latter  body  is  sub- 
jected to  the  action  of  certain  salts,  it  loses  the  elements  of 
water  and  is  converted  into  a  body  which  Lieben  called  acral- 
dehyde,  but  which  is  no  other  than  crotonic  aldehyde. 

2C2H40  =  C4H60  +  H20 

This  aldehyde  is  a  liquid  having  a  very  irritating  odor  and 
an  acrid  taste.  It  boils  at  103°. 

When  submitted  to  the  action  of  oxidizing  agents,  such  as 


POLYATOMIC   COMPOUNDS — ETHYLENE.  513 

silver  oxide  in  presence  of  water,  it  is  converted  into  crotonic 
acid. 

C*H60  -f  0  =  C4H602 

Three  isomeric  modifications  of  this  acid  are  known.     One 
is  liquid,  the  others  are  solid. 


POLYATOMIC    COMPOUNDS. 

After  the  description  of  the  comparatively  simple  compounds 
which  are  naturally  grouped  with  the  monatomic  alcohols,  we 
proceed  to  the  more  complex  compounds  constituting  the  poly- 
atomic alcohols  and  their  derivatives.  The  latter  alcohols  are 
neutral  hydrates,  capable  of  reacting  with  the  acids  to  form  neu- 
tral combinations  analogous  to  the  compound  ethers.  Those 
better  known  are  related  to  the  saturated  hydrocarbons,  from 
which  they  are  derived  by  the  substitution  of  several  hydroxyl 
groups  for  as  many  atoms  of  hydrogen. 


OH10  C«HU 

Ethane.                          Propane.                     Butane.  Hexane. 

C2H*(OH)2                C3H5(OH)3            C*H6(OH)*  C6H8(OH)S 

Ethylene  dihydrate            Glyceryl  tri-               Erythrite.  Mannite. 
(glycol).               hydrate  (glycerin). 

By  oxidation  of  these  polyatomic  alcohols,  polyatomic  acids 
are  produced  which  bear  the  same  relation  to  the  former  that 
acetic  acid  bears  to  ordinary  alcohol. 

It  will  be  noticed  that  the  radicals  of  these  alcohols  are  un- 
saturated  hydrocarbons,  that  is,  they  contain  less  hydrogen  than 
the  saturated  hydrocarbons,  CnH2n+2.  Of  these  radicals,  only 
those  can  exist  in  a  free  state  which  contain  an  even  number 
of  atoms  of  hydrogen.  We  will  briefly  consider  the  more 
important  of  them. 

ETHYLENE. 
C2H*  =  CH2=CH* 

This  gas,  formerly  known  as  olefiant  gas  or  heavy  carbu- 
retted  hydrogen,  is  formed  in  a  great  number  of  reactions.  It 
is  produced,  together  with  other  hydrocarbons,  when  substances 
rich  in  carbon  and  hydrogen,  such  as  fats  and  resins,  arc  de- 
composed by  dry  distillation,  that  is,  by  the  destructive  action 
of  heat. 
w* 


514  ELEMENTS   OF   MODERN   CHEMISTRY. 

Preparation. — It  is  obtained  in  the  laboratory  by  dehydrat- 
ing alcohol  by  a  large  excess  of  sulphuric  acid.  Ordinarily,  a 
mixture  of  one  part  of  alcohol  and  4  parts  of  concentrated  sul- 
phuric acid  is  heated  in  a  flask  containing  almost  enough  sand 
to  absorb  the  entire  liquid.  The  gas  disengaged  is  passed 
through  a  wash-bottle  containing  potassium  hydrate,  and  may 
then  be  collected  over  water. 

Towards  the  close  of  the  operation  the  liquid  blackens,  and 
much  sulphurous  and  carbonic  acid  gases  are  disengaged. 
These  are  absorbed  by  the  potassa  in  the  wash-bottle. 

The  following  equation  expresses  the  reaction  by  which 
ethylene  is  formed : 

C2H60  ==  C2H4  +  H20 

Composition  and  Properties. — Ethylene  is  a  colorless  gas, 
having  a  feeble,  ethereal  odor.  Its  density  is  0.9784  compared 
to  air,  or  14  compared  to  hydrogen. 

Its  composition  may  be  deduced  from  the  following  experi- 
ment: 

2  volumes  of  ethylene  (2  cubic  centimetres,  for  example) 
and  6  volumes  of  oxygen  are  introduced  into  an  eudiometer 
over  mercury.  After  the  passage  of  the  spark,  the  8  volumes 
will  be  found  to  be  reduced  to  4  volumes,  all  of  which  will  be 
entirely  absorbed  if  a  solution  of  potassium  hydrate  be  passed 
into  the  tube.  The  4  volumes  are  therefore  carbon  dioxide. 

4  volumes  of  carbon  dioxide  represent  2C02. 

2  volumes  of  ethylene  therefore  contain  C2. 

4  volumes  of  carbon  dioxide  contain  but  4  of  the  6  volumes  of  oxygen 
employed ;  the  other  two  have  therefore  been  used  in  the  formation  of 
water  and  have  burned  4  volumes  of  hydrogen. 

2  volumes  of  ethylene  then  contain  4  volumes  of  hydrogen. 

Eudiometric  analysis  therefore  indicates  the  composition  of 
ethylene  to  be 

C2H4  ==  2  volumes. 

This  gas  is  inflammable  and  burns  in  the  air  with  a  brill- 
iant flame.  When  mixed  with  three  volumes  of  oxygen  and 
ignited,  it  produces  a  violent  explosion. 

It  is  slowly  absorbed  by  concentrated  sulphuric  acid,  ethyl- 
sulphuric  acid  being  formed.  When  ethylene  is  heated  with 
hydriodic  acid,  the  two  bodies  combine  directly  to  form  ethyl 
iodide. 

If  one  volume  of  ethylene  and  two  volumes  of  chlorine  be 


ETHYLENE.  515 

rapidly  mixed  in  a  tall  jar,  and  a  lighted  match  be  applied,  the 
mixture  takes  fire  and  burns  with  a  red  flame  extending  to  the 
bottom  of  the  jar,  which  becomes  covered  with  a  black  deposit 
of  carbon. 

C2H4  +  2CF  =  4HC1  +  C2 

If  equal  volumes  of  ethylene  and  chlorine  be  mixed  and  ex- 
posed to  diffused  light  on  the  pneumatic  trough,  the  water  will 
soon  rise  in  the  jar,  and  the  two  gases  will  disappear.  At  the 
same  time,  oily  drops  will  appear  on  the  sides  of  the  jar  and 
upon  the  surface  of  the  liquid.  The  body  so  formed  is  a  liquid 
insoluble  in  water,  and  results  from  the  direct  combination  of 
ethylene  and  chlorine.  It  was  formerly  called  Dutch  liquid, 
or  Dutch  oil  (hence  the  old  name  olefiant  gas)  ;  it  is  now  called 
ethylene  chloride.  Its  composition  is  expressed  by  the  formula 
C2H4CP.  It  boils  at  82.5°. 

If  a  small  quantity  of  bromine  be  poured  into  a  large  flask 
filled  with  ethylene.  and  manipulated  so  that  the  bromine  may 
form  a  thin  layer  on  the  sides  of  the  flask,  an  elevation  of  tem- 
perature will  be  observed,  and  the  liquid  will  rapidly  become 
colorless.  The  bromine  has  combined  with  the  ethylene  to 
form  a  colorless  liquid,  ethylene  bromide,  boiling  at  131°. 

Ethylene  iodide,  C2H4P,  may  be  obtained  by  introducing 
iodine  into  large  jars  filled  with  ethylene,  and  exposing  to  dif- 
fused light  during  several  days.  The  iodine  is  little  by  little 
converted  into  a  solid,  white  body,  which  may  be  purified  by 
crystallization  in  alcohol ;  it  is  ethylene  iodide. 

Chloro-Derivatives  of  Ethylene  and  Ethylene  Chloride. — 
If  ethylene  chloride  be  heated  with  an  alcoholic  solution  of 
potassium  hydrate,  a  brisk  reaction  soon  takes  place.  A  gas 
is  disengaged  and  may  be  collected  over  water ;  on  contact 
with  a  lighted  taper,  it  burns  with  a  flame  tinged  with  green. 
This  gas  is  chlor ethylene.  It  is  formed  according  to  the  fol- 
lowing equation : 

C2H4CP  +  KOH  =  H'O  +  KC1  +  C2H3C1 

Like  ethylene  itself,  chlorethylene  will  combine  directly  with 
two  atoms  of  chlorine,  forming  chlorethylene  chloride,  C2H3C1. 
CP,  which  may  also  be  obtained  by  the  action  of  chlorine  on 
ethylene  chloride. 

Chlorethylene  chloride  is  decomposed  by  alcoholic  potassa, 
like  ethylene  chloride.  Water,  potassium  chloride,  and  dichlor- 
ethylene  are  formed. 


516  ELEMENTS   OP   MODERN    CHEMISTRY. 

C2H3CP     -f  KOH  ==  H20  +  KC1  +     C2H2C12 

Chlorethylene  chloride.  Dichlorethylene. 

In  its  turn,  dichlorethylene  can  fix  two  atoms  of  chlorine, 
forming  dichlorethylene  chloride. 

These  reactions  have  permitted  the  preparation  of  two 
classes  of  chloro-compounds, — one  derived  from  ethylene  chlo- 
ride, the  other  from  ethylene  itself. 

DENSITIES.  BOILING-POINTS. 

C2H4C13  ethylene  chloride.  1.256  at  12°  82.5° 

C2H3C13  chlorethylene  chloride.  1.422  at  17°  115° 

C2H2C1*  dichlorethylene  chloride.  1.576  at  19°  137° 

C2HC15   trichlorethylene  chloride.  158° 

C2C16      carbon  sesquichloride.  182° 


C2H4        ethylene. 

C2H3C1   chlorethylene.  —18  to  —15° 

C2H2C12  dichlorethylene.  1.250  at  14°  35  to  40° 

C2HC13   trichlorethylene.  87  to  88° 

C2C14       tetrachlorethylene.  2.619  at  20°  116.7° 

Regnault,  who  carefully  studied  these  bodies,  has  shown 
that  the  terms  of  the  first  series  are  isomeric  with  the  chloro- 
derivatives  of  ethyl  chloride,  with  the  exception  of  the  last 
two,  which  are  the  same  in  both  series. 

That  we  may  more  thoroughly  understand  this  isomerism, 
we  will  consider  ethylene  chloride,  C2H4CP,  and  its  isomeride 
dichlorethane,  called  also  ethylidene  chloride.  In  the  first, 
two  atoms  of  chlorine  are  united,  each  to  a  different  atom  of 
carbon  ;  in  the  second,  both  are  united  to  the  same  carbon 
atom. 

CH2C1  CHCI2 

CH2C1  CH3 

Ethylene  chloride.  Ethylidene  chloride. 

Tetrachlorethylene  was  discovered  by  Faraday  in  1821.  It 
is  formed  by  the  action  of  alcoholic  potassium  hydrate  on  tri- 
chlorethylene chloride. 

C2HCP  =  C2C14  +  HC1 

It  is  also  formed  by  the  action  of  a  red  heat  on  carbon 
sesquichloride. 


It  is  a  very  mobile  liquid,  which  does  not  solidify  at  —  18°. 
It  absorbs  chlorine  under  the  influence  of  direct  sunlight,  being 
transformed  into  carbon  sesquichloride,  C2C16. 


HOMOLOGOUS    SERIES,  CnH2n.  517 


HOMOLOGOUS   SERIES,  CnH2n 

Ethylene  is  the  first  member  of  a  rich  series  of  homologues, 
of  which  we  will  summarily  describe  a  few  of  the  others.  It 
is,  however,  important  to  remark  that  since  ethylene  is  (CH2)2, 
it  would  seem  that  the  constitution  of  the  superior  hydrocar- 
bons of  the  series  should  be  expressed  by  the  formula  (CH2/1. 
Thus  far  none  of  these  normal  hydrocarbons  have  been  isolated. 
For  example,  normal  propylene,  CH2-CH2-CH2,  is  unknown. 
The  compound  C3H6,  which  will  shortly  be  described,  is  an 
isomeride  of  normal  propylene,  and  its  constitution  is  expressed 
by  the  formula  CH3-CH=CH2.  It  absorbs  chlorine  directly, 
forming  the  chloride 

CH3-CHC1-CH2C1 

Above  the  fourth  member  of  this  series,  butylene,  the 
number  of  isomerides  increases  rapidly.  Thus,  the  butylene 
derived  by  dehydration  from  butyl  alcohol  of  fermentation  is 


It  is  formed  according  to  the  following  reaction  : 
—  H20  = 


Independently  of  this  butylene,  there  are  two  others,  the 
formation  and  principal  properties  of  which  will  be  indicated 
farther  on. 

Their  constitutions  are  expressed  by  the  formulae 

CHa-CH=CH-CH3 
CH3-CH2-CH=CIP 

The  isomeric  relations  of  these  three  butylenes  may  be  repre- 
sented in  a  very  simple  manner  if  we  consider  them  to  be 
derived  from  ethylene,  H2C=CH2,  the  hydrogen  of  which  is 
partly  replaced  by  methyl  or  ethyl.  The  following  compounds 
are  thus  obtained  : 

Dimethylethylene  a  (CH3)2C=CH2,  boils  at  —6°. 

Dimethylethylene  ft  (normal)        (CH3)HC=CH(CH3),  boils  at  +3°. 
Ethylethylene  (C2H5)HC=CH2,  boils  at  —5°. 

The  fifth  member  of  the  series,  amylene  or  pentene,  C5H10, 
presents  still  more  numerous  isomerides,  but  they  can  all  be 
explained  by  the  principles  already  exposed  :  they  may  be  re- 

44 


518  ELEMENTS    OP    MODERN    CHEMISTRY. 

garded  as  derivatives  of  ethylene  by  the  substitution  of  a  pro- 
pylic  or  isopropylic  group  for  one  atom  of  hydrogen,  or  by  the 
substitution  of  an  ethyl  group  and  a  methyl  group  for  two 
atoms  of  hydrogen,  or  lastly,  by  the  substitution  of  three  methyl 
groups  for  three  atoms  of  hydrogen. 

Propylene,  C3H6. — To  prepare  this  gas  in  a  pure  state  Ber- 
thelot  and  de  Luca  heat  allyl  iodide  with  mercury  and  concen- 
trated hydrochloric  acid. 

2C3H5I  +  4Hg  +  2HC1  =  Hg2CP  +  Hg2!2  +  2C3H6 

Propylene  is  a  colorless  gas,  having  a  feeble,  alliaceous  odor. 
It  is  rapidly  absorbed  by  sulphuric  acid,  with  formation  of 
isopropylsulphuric  acid  (Berthelot). 

C3H6  +  H2SO*  = 

It  unites  directly  with  hydriodic  acid,  forming  an  iodide 
which  is  isomeric  with  propyl  iodide. 

C3H6  +  HI  =  (C3H7)SI 

Propylene  unites  directly  with  chlorine  and  bromine,  forming 
propylene  chloride,  C3H6C12,  and  propylene  bromide,  C3H6Br2. 
The  latter  is  a  colorless  liquid,  boiling  at  145°. 

The  propylene  just  described  is  not  normal  propylene,  (CH2)3. 
Its  constitution  and  that  of  its  bromide  are  expressed  by  the 
formulae 

CH3-CH=CH2  CH3-CHBr-CH2Br 

Propylene.  Propylene  bromide. 

Normal  propylene  is  not  known,  but  the  corresponding  bro- 
mide exists.  It  has  been  obtained  by  heating  allyl  bromide, 
C3H5Br,  with  hydrobromic  acid. 

CH2=CH-CH2Br    +    HBr   =    CH2Br-CH2-CH2Br 

Allyl  bromide.  Normal  propylene  bromide. 

The  latter  bromide  is  a  colorless  liquid,  boiling  at  165°. 

BUTYLENES,  C4H8. 

1.  Dimethylethylene  «,  (CH3)2C=CH2.  —  This  body  is 
formed  when  isobutyl  alcohol  is  dehydrated  by  zinc  chloride, 
or  by  the  action  of  alcoholic  potassium  hydrate  xm  butyl  iodide, 
C4H9L  It  boils  at  — 6°.  It  unites  directly  with  hydriodic  acid, 
forming  tertiary  butyl  iodide,  (CH3)2CI-CH3,  and  combines 


AMYLENES.  519 

with  bromine,  forming  the  bromide  (CH3)2CBr-CH2Br,  which 
boils  at  149°. 

2.  Dimethylethylene  /?,  (normal  or  symetric)  (CH3)HC= 
CH(CH3). — Is  formed  by  the  action  of  alcoholic  potassa  on 
secondary  butyl  iodide,  CH3-CH2-CHI-CH3.     Boils  at  +3° 
and  solidifies  to  a  crystalline  mass  at  0°.     Unites  with  HI, 
regenerating  secondary  butyl  iodide,  and  with  bromine,  forming 
the  bromide  (CH3)HBrC-CHBr(CH3),  which  boils  at  159°. 

'  De  Luynes  obtained  secondary  butyl  iodide  by  reducing 
erythrite  with  a  large  excess  of  hydriodic  acid  (page  565). 

3.  Ethylethylene  (ethyl-vinyl),  (C2H3)HC-CH2.— Is  ob- 
tained by  the  action  of  sodium  on  a  mixture  of  ethyl  iodide 
and  bronethylene. 

C2H5I  +  BrIIC=CH2  +  Na2  =  Nal  +  NaBr  +  (C2H5)IIC=CII2 

Boiling-point,  — 5°.  It  unites  with  HI,  forming  secondary 
butyl  iodide,  and  with  bromine,  forming  the  bromide  CH3— 
CH2-CHBr-CH2Br,  boiling  at  166°. 

AMYLENES,   OR  PENTENES,  C5H10. 

Several  isomeric  hydrocarbons  are  known  of  the  composition 
C5H10.  They  exist  in  unequal  proportions  in  the  product  of 
the  reaction  of  zinc  chloride  on  amyl  alcohol,  a  product  gener- 
ally designated  as  amylene.  It  is  prepared  by  heating  amyl 
alcohol  with  zinc  chloride,  and  passing  the  vapors  which  are 
given  off  into  a  well-cooled  receiver.  The  product  is  rectified, 
that  portion  being  retained  which  passes  below  40°.  It  is  a 
mixture  of  isomeric  amylenes,  whose  boiling-points  vary  from 
22  to  40°,  and  which  result  from  the  dehydration  of  amyl 
alcohol. 

We  need  only  describe  two  of  these  isomeric  hydrocarbons: 
trimethylethylene,  which  constitutes  the  greater  portion  of  the 
mixture,  and  isopropylethylene. 

Trimethylethylene  or  ordinary  amylene  may  be  obtained  in 
a  pure  state  by  dehydrating  tertiary  amyl  alcohol  (the  hydrate 
of  amylene  of  Wurtz),  which  may  be  accomplished  by  simply 
heating  it. 

(CH3)2=C(OH)-CH2-CH3  —  H2Q    =    (CH»)*G=CH(CHij 

Tertiary  amyl  alcohol.  Trimethylethylene. 

It  boils  at  36°,  and  unites  directly  with  hydriodic  acid,  form- 
ing tertiary  amyl  iodide,  (CH3)2CI-CH2-CH3,  which  boils  at 
129°. 


520  ELEMENTS    OP    MODERN   CHEMISTRY. 

When  bromine  is  poured  into  cooled  amylene,  the  addition 
of  each  drop  produces  a  hissing  noise,  indicating  a  violent  reac- 
tion, and  the  product  is  a  liquid  amylene  bromide,  boiling  be- 
tween 1*70  and  180°.  If  the  operation  be  performed  upon  crude 
amylene,  a  mixture  of  several  bromides  will  result.  Trimethyl- 
ethylene  yields  a  bromide  containing  (CH3)2^CBr-CHBr-CH3. 

Isopropylethylem  is  formed  by  the  action  of  alcoholic  potas- 
sium hydrate  on  amyl  iodide  (Flavitzky). 

cJ*3>CH-CH2-CH2I  —  HI   =  CH3>CH-C1I=CH2 
Amyl  iodide.  Isopropyletliylene. 

This  body  also  exists  in  small  quantity  in  the  mixture  of 
hydrocarbons  formed  by  the  action  of  zinc  chloride  on  amyl 
alcohol.  Boiling-point,  25°.  It  unites  with  hydriodic  acid, 
forming  a  secondary  iodide,  (CH3)2^CH-CHI-CH3,  which  boils 
at  137-139°.  It  combines  with  bromine,  forming  the  bromide 
(CH3)2=CH-CHBr-CH2Br,  which  boils  between  180  and  190°. 

Polymerides  of  Amylene.  —  By  the  action  of  zinc  chloride 
on  amyl  alcohol,  there  are  formed,  independently  of  amylene, 
other  hydrocarbons,  among  which  are  the  polymeric  modifica- 
tions known  as  diamylene,  C10H20;  triamylene,  C13!!30  ;  tetra- 
mylene,  C20H40  (Balard,  Bauer).  These  bodies  are  formed  by 
the  union  of  one,  two,  three,  or  four  molecules  of  amylene. 

HYDROCARBONS  OF  THE  SERIES  CnH2"-2. 

Among  the  more  simple  hydrocarbons  is  one  which  was  dis- 
covered by  E.  Davy,  and  which  Berthelot  has  recently  suc- 
ceeded in  preparing  by  various  processes.  It  is  acetylene,  and 
is  the  first  member  of  a  series  which  includes,  among  others, 
the  following  hydrocarbons  : 

Acetylene      C2H2  (E.  Davy,  Berthelot). 
Allylene        C3H4  (Sawitsch). 
Crotonylene  C4H6  (E.  Caventou). 
Valerylene    (W  (Reboul). 


Acetylene,  C2H2  =  CH^CH.—  This  gas  is  produced  by  the 
incomplete  combustion  of  many  organic  substances  rich  in  car- 
bon (Berthelot). 

If  a  few  drops  of  ether  be  poured  upon  the  surface  of  an 
ammoniacal  solution  of  cuprous  chloride  contained  in  a  nar- 
row jar,  and  its  vapor  be  ignited,  a  brownish-red  deposit  of 
acetylenide  of  copper  will  be  formed  and  may  be  observed  on 


DIATOMIC   ALCOHOLS.  521 

flowing  the  liquid  around  on  the  sides  of  the  jar.  This  reac- 
tion is  characteristic  of  acetylene. 

This  gas  may  be  formed  by  the  direct  union  of  carbon  and 
hydrogen,  as  discovered  by  Berthelot,  when  the  electric  arc  is 
passed  between  carbon  points  in  a  vessel  containing  pure  hydro- 
gen. At  the  high  temperature  of  the  arc,  the  hydrogen  com- 
bines directly  with  the  carbon,  forming  acetylene. 

It  is  also  formed  when  inonobromethylene  is  heated  with 
amylate  of  sodium  (the  sodium  compound  of  amyl  alcohol) 
(Sawitsch). 

C2H3Br  +    C5Hn.ONa    =    C2H2    +    C5Hn.OH  +  NaBr 

Mouobrom-         Amylate  of  sodium.        Acetylene.  Amyl  alcohol, 

ethylene. 

Acetylene  is  a  colorless  gas,  having  a  peculiar  and  disagree- 
able odor.  It  is  quite  soluble  in  water.  It  burns  with  a  bright 
but  smoky  flame.  It  forms  two  compounds  with  bromine,  a 
dibromide,  C2H'W,  and  a  tetrabromide,  C2H2Br4. 


DIATOMIC  ALCOHOLS,  OR  GLYCOLS. 

The  name  glycols  was  given  by  Wurtz  to  the  dihydrates  of 
the  series  of  hydrocarbons,  CnH2n.  If  ordinary  alcohol  be 
ethyl  hydrate,  ordinary  glycol  is  ethylene  dihydrate. 

C2H5.OH  C2H4(OH)2 

Ethyl  hydrate.  Ethylene  dihydrate. 

While  alcohol  reacts  with  a  single  molecule  of  a  monobasic 
acid  to  form  a  neutral  ether,  glycol  can  react  with  either  one 
or  two  molecules  of  a  monobasic  acid,  thus  forming  two  ethers. 
In  other  words,  while  the  monatomic  alcohols  contain  but  one 
atom  of  hydrogen  which  is  replaceable  by  a  single  radical  of  a 
monobasic  acid,  glycol  contains  in  the  two  groups  OH  two  such 
atoms  of  hydrogen,  capable  of  being  replaced  by  2  radicals  of 
a  monobasic  acid,  or  one  radical  of  a  dibasic  acid. 


(C*H*02)" 
Ethyl  acetate.  Ethylene  diacetate.  Ethylene  succinate. 

The  glycols  yield  diatomic  acids  by  oxidation. 
There  are  isomeric  glycols,  or  isoglycoh,  corresponding  to 
the  isoalcohols  which  have  already  been  denned  (page  473). 

44* 


522  ELEMENTS   OP   MODERN   CHEMISTRY. 

Six  glycols  are  now  known,  belonging  to  the  series  CnH2n+202. 

DENSITY  AT  0°.     BOILING-POINTS. 

Ethylene  glycol,  or  glycol      .     .     .  C2H602  1.125  197.5° 

Propylene  glycol,  or  propylglycol  .  C3H802  1.051  188-189° 

Butylene  glycol,  or  butylglycol     .  C4Hi°02  1.048  183-184° 

Amylene  glycol,  or  auiylglycol  .     .  C5111202  0.987  177° 

Hexylene  glycol,  or  hexylglycol     .  C6HU02  0.9667  207° 

Octylene  glycol,  or  octylglycol  (Ph. 

de  Clermont)   .......  C8H1602 

It  is  to  be  remarked  that  all  of  the  members  of  the  above 
series  are  not,  strictly  speaking,  homologous. 

The  structure  of  the  latter  glycols  is  different  from  that 
of  ethylene  glycol  ;  they  are  isoglycols.  The  propylglycol 
discovered  by  Wurtz  is  of  this  number.  Normal  propylglycol 
has  recently  been  discovered  by  Geroinont,  and  obtained  in  a 
pure  state  by  Reboul. 

The  isomerism  of  the  glycols,  like  that  of  the  alcohols,  is 
due  to  the  constitutions  of  their  molecules,  which  can  contain, 
like  the  molecules  of  the  alcohols,  the  following  groups  : 

The  primary  group  -CH2.OH 
The  secondary  group  =CH.OH 
The  tertiary  group  ^C. 


Thus,  ethylene  glycol  is  primary,  since  it  contains  two  groups, 
CH2.OH. 

The  amylglycol  derived  from  trimethylethylene  is  at  the 
same  time  secondary  and  tertiary. 

Pinacone,  which  has  already  been  mentioned  (page  504),  is 
a  tertiary  glycol;  it  contains  two  groups  ^(C.OH). 

CH2.OH                  CH3>  C>OH  J^  f  '°H 

CH2.0H                        CH3-CH.OH  CH»>  C'OH 

Glycol.                               Amylglycol.  Pinacone. 

(Secondary  and  tertiary.)  (Tertiary.) 

Among  the  mixed  glycols,  that  is,  those  containing  at  the 
same  time  two  different  alcoholic  groups,  is  ordinary  propyl- 
glycol, which  is  primary  and  secondary. 

CH2.OH  CH3 

CH2  CH.OH 

CH2.OH  CH2.0H 

Normal  propylglycol.  Ordinary  propylglycol. 

(Primary).  (Primary  and  secondary). 


GLYCOL.  523 


GLYCOL,   OR  ETHYLENE   DIHYDRATE. 

C2H6O2  =  C2H*(OH)2 

Wurtz  first  obtained  glycol  by  causing  either  iodide  or  bro- 
mide of  ethylene  to  react  with  silver  acetate 

,    Ag.C2H302  rrzmy  I  C2H302  „.    T 

CtH*P  +  A=<C2H302  >    1C2H302    ' 

Silver  acetate.  Ethylene  diucetate. 

and  saponifying  the  resulting  ethylene  diacetate  by  potassium 
hydrate. 


+  2KOH   =  2(C2H30.0K)  +  (C*H*)" 
Ethylene  diacetate.  Potassium  acetate.  Glycol. 

Atkinson  has  shown  that  the  silver  acetate  may  be  advan- 
tageously replaced  by  an  alcoholic  solution  of  potassium  ace- 
tate. Bromide  of  ethylene  reacts  with  the  latter  salt,  forming 
potassium  bromide,  which  is  almost  insoluble  in  alcohol,  and 
ethylene  acetate  which  is  afterwards  decomposed  by  caustic 
potassa  or  caustic  baryta. 

Another  process  has  been  recently  proposed  by  Hiifner  and 
Zoller.  188  grammes  of  ethylene  bromide,  138  grammes  of 
potassium  carbonate  and  1  litre  of  water  are  introduced  into  a 
large  flask  connected  with  a  reversed  condenser,  and  the  mix- 
ture is  boiled  until  all  of  the  ethylene  bromide  has  disappeared. 
The  aqueous  liquid  is  then  concentrated  on  a  water-bath,  and 
alcohol  is  added  to  precipitate  the  potassium  bromide  ;  the 
alcoholic  liquid  is  then  distilled.  Alcohol  and  water  first  pass, 
and  when  the  temperature  rises  above  150°,  the  liquid  which 
condenses  is  nearly  pure  glycol. 

Properties.  —  Grlycol  is  a  somewhat  syrupy,  colorless,  and 
odorless  liquid,  having  a  sweet  taste.  It  mixes  with  water  and 
alcohol  in  all  proportions,  but  is  scarcely  soluble  in  ether.  It 
boils  at  197.5°,  and  distils  without  alteration. 

Its  analogy  to  alcohol,  from  which  it  differs  by  containing 
one  more  atom  of  oxygen,  is  demonstrated  by  the  following 
experiments  : 

1.  If  platinum  black  be  moistened  with  glycol  and  then 
rapidly  plunged  into  a  jar  of  oxygen,  a  brilliant  incandes- 
cence is  manifested  immediately,  due  to  the  energetic  absorp- 
tion of  oxygen. 


524  ELEMENTS   OP   MODERN   CHEMISTRY. 

With  dilute  glycol,  the  oxidation  is  slower,  and  glycollic  acid 
is  formed. 

CH2.0II  CH2.OH 

CH2.0H   +     °2  =     CO.OH    +    I12° 
Glycol.  Glycollic  acid. 

2.  If  glycol  be  heated  with  ordinary  nitric  acid,  torrents  of 
red  vapor  are  disengaged,  and  the  liquid  deposits  crystals  of 
oxalic  acid  on  cooling. 

CH2.0H  CO.OH 

CIP.OH    +  202  =  CO.OH    +2I12° 
Glycol.  Oxalic  acid. 

3.  When  glycol  is  heated  with  potassium  hydrate  to  250°, 
pure  hydrogen  is  disengaged  and  potassium  oxalate  is  formed. 

C2H602  -f  2KOH    =   C'OK2   -f   4H2 

Glycol.  Potassium  oxalate. 

These  experiments  establish  between  glycol  and  glycollic  and 
oxalic  acids,  relations  analogous  to  those  which  exist  between 
alcohol  and  acetic  acid. 

Ethylene  Chlorhydrate,  or  Ethylenic  Chlorhydrin.  — 
When  hydrochloric  acid  gas  is  passed  into  glycol,  a  neutral 
compound  is  formed  which  constitutes  the  monochlorhydrm 
of  glycol,  or  ethylene  chlorhydrate. 

C2H*<^    +     HC1   =    C2H4<J^    +    H20 

Glycol.  Ethylene  chlorhydrate. 

This  compound  is  intermediate  between  glycol  and  ethylene 
chloride,  which  is  the  dichlorhydrin  of  glycol. 


Glycol.  Monochlorhvdrin  of  Dichlorhydrin  of  yrlycol 

glycol.  (ethylene  chloride). 

Ethylene  chlorhydrate  is  also  formed  by  the  direct  union  of 
ethylene  gas  and  hypochlorous  acid  (Carius). 

C2^  -f  HC10  ==  C2H5C10 

It  is  a  colorless  liquid,  having  a  density  of  1.24  at  8°.  It 
boils  at  130-131°. 

Ethylene  bromhydrate,  or  etliylenic  bromJiydrin,  is  formed 
under  circumstances  analogous  to  those  which  furnish  the 
chlorhydrate.  It  is  a  thick,  colorless  liquid,  boiling  at  147°. 


ETHYLENE   OXIDE.  525 

Ethylene  Nitrates.  —  By  the  reaction  of  ethylene  brom- 
hydrate  on  silver  nitrate,  at  ordinary  temperatures  or  by  the 

0  NO2 

aid  of  gentle  heat,  ethylene   mononitrate,   C2H*<C/-vir      >  *s 

obtained  as  a  colorless  or  slightly  yellow  liquid,  which  is  sol- 
uble in  water.     Density  at  11°,  1.31. 

Ethylene  dinitrate,  C2H4<'™,  is  formed  by  the  action 


of  ethylene  bromide  on  an  alcoholic  solution  of  silver  nitrate. 
It  is  a  mobile,  colorless  liquid,  insoluble  in  water.  Density  at 
8°,  1.4837.  It  explodes  by  percussion  (Henry). 

Ethylene  Acetates.  —  When  glycol  is  heated  with  acetic 
acid,  it  is  converted  into  acetic  ethers. 


C2H3Q.OH    = 

Acetic  acid.  Ethylene  monacetate. 


C2H4<OH 

Acetic  acid.  Ethylene  diacetate. 

Ethylene  monacetate,  or  monacetic  glycol,  is  a  liquid  mis- 
eible  with  water  and  alcohol,  and  boiling  at  182°. 

Ethylene  diacetate,  or  diacetic  glycol,  can  be  prepared  by  the 
reaction  of  ethylene  iodide  on  silver  acetate.  It  is  a  colorless 
liquid,  soluble  in  7  parts  of  water  ;  it  boils  at  186°. 

It  is  thus  seen  that  two  neutral  ethereal  compounds  can  be 
formed  by  the  action  of  one  and  the  same  monobasic  acid  on 
glycol,  while  the  monatomic  alcohols  would  furnish  but  a  single 
compound  ether  under  the  same  circumstances. 

ETHYLENE   OXIDE. 
CH2 


If  an  excess  of  potassium  hydrate  be  added  to  ethylene 
chlorhydrate  contained  in  a  test-tube,  and  a  gentle  heat  be 
applied,  a  brisk  effervescence  will  take  place,  due  to  a  dis- 
engagement of  vapor  which  may  be  ignited  at  the  mouth  of 
the  tube. 

At  a  low  temperature,  this  vapor  condenses  to  a  colorless 
liquid,  which  is  ethylene  oxide. 

C2H5C10       =       C2H4O       +       HC1 

Ethylene  chlorhydrate.          Ethylene  oxide. 


526  ELEMENTS   OF   MODERN    CHEMISTRY. 

Ethylene  oxide  has  the  composition  of  glycol,  less  the  ele- 
ments of  one  molecule  of  water. 

C2H*0  ==  C2H602  —  H20 

However,  it  cannot  be  obtained  by  direct  dehydration  of 
glycol,  for  when  that  body  is  distilled  with  zinc  chloride, 
among  other  products,  aldehyde,  which  is  isonaeric  with  ethyl- 
ene  oxide>  is  obtained. 

Greene  has  obtained  ethylene  oxide  by  double  decomposi- 
tion, by  heating  ethylene  bromide  with  anhydrous  sodium 
oxide. 

C2HW  +  Na20  =  C2H40  +  2NaBr 

Properties. — Ethylene  oxide  boils  at  13.5°.  It  dissolves 
in  all  proportions  in  water,  alcohol,  and  ether.  Under  the 
influence  of  sodium  amalgam  and  water,  it  fixes  hydrogen 
directly,  being  transformed  into  alcohol. 

C2H40  +  H2  =  C2H60 

It  combines  directly  with  water  at  100°,  regenerating  glycol. 
C2H40  -f  H20  =  C2H602 

It  possesses  basic  properties. 

If  equal  volumes  of  hydrochloric  gas  and  vapor  of  ethylene 
oxide  be  mixed  over  the  mercury-trough  (the  mercury  should 
be  slightly  warmed)  the  two  gases  will  disappear ;  they  combine 
to  form  a  liquid  which  is  ethylene  chlorhydrate. 
C2H40  +  HC1  =  C2H5C10 

If  liquid  ethylene  oxide  be  added  to  a  cooled  solution  of 
magnesium  chloride,  an  abundant  precipitate  of  magnesium 
hydrate  will  be  formed  in  the  course  of  a  day,  and  the  liquid 
will  contain  ethylene  chlorhydrate.  Oxide  of  ethylene  precipi- 
tates magnesia  as  would  a  powerful  base  (A.  Wurtz). 

If  a  fragment  of  zinc  chloride  be  allowed  to  fall  into  ethylene 
oxide,  the  latter  soon  undergoes  a  curious,  polymeric  change, 
and  becomes  solid  (A.  Wurtz). 

Eases  Derived  from  Ethylene  Oxide. — Oxide  of  ethylene 
combines  with  ammonia,  yielding  a  series  of  bases,  the  hydrox- 
ethylenamines,  which  are  formed  by  the  direct  union  of  one, 
two,  or  three  molecules  of  ethylene  oxide  with  one  molecule  of 
ammonia. 

C2H4.OH  )  C2H*.OH ")  C2H*.OH  ) 

H  V  N  C2H*.OH  [  N  C2H*.OH  [•  N 

Hj  H)  C'HiOHj 

Hydroxethylenamine.  Dihydroxethylenamine.  Trihydroxethylenaraine. 


ETHYLENE-DIAMINES.  527 

These  bases  are  also  formed  by  the  action  of  ammonia  on 
ethylene  chlorhydrate. 


) 

+     NH3    =  H  V  N      +     HC1 

HJ 

When  ethylene  chlorhydrate  is  treated  with  trimethylamine, 
the  bodies  combine,  forming  a  chloride. 


When  this  chloride  is  treated  with  water  and  silver  oxide, 
it  is  converted  into  a  hydrate. 

C*H*.OH) 


This  hydrate  is  neurine,  an  energetic  natural  base  which 
exists  in  the  bile  (choline)  and  which  is  also  a  product  of  the 
decomposition  of  a  complex  substance,  leeithine,  which  exists 
in  the  brain,  in  the  nerves,  and  in  the  yolk  of  eggs. 


ETHYLENE-DIAMINES. 

These  bases  result  from  the  substitution  of  one,  two,  or  three 
ethylene  groups,  (C2H4)",  each  for  two  atoms  of  hydrogen  in 
two  molecules  of  ammonia. 

They  are  formed  by  the  reaction  of  an  alcoholic  solution  of 
ammonia  on  ethylene  bromide  at  ordinary  temperatures. 

C2H4Br2     +     2NH3    =     C2H4(NH2)2.2HBr 

Ethylene-dlamine 
hydrobromide. 

CH2-NH'  f  (C»H*)"  . 

Etnylene-diamme,  ^H2_NH2  =N*  {  B          ls  a  hquld  b^6? 

boiling  at  123°.  By  the  prolonged  action  of  an  excess  of 
ethylene  bromide,  it  is  converted  successively  into  dieihylene- 
diamine  and  triethylene-diamine. 

(C2H*)"  f(C2H4)"  f(C2H4)" 


Ethylene-diamine.  Diethylene-diamine.  Triethylene-diamine. 

Diethylene-diamine  boils  at  1*70°,  and  triethylene-diamine  at 
210°.  They  are  liquids.  The  ethlylene-diamines  are  diacid, 
that  is,  they  combine  with  two  molecules  of  a  monatomic  acid, 
such  as  hydrochloric  or  hydrobromic  acid  (Hofmann). 


528  ELEMENTS   OF   MODERN   CHEMISTRY. 

ISETHIONIC   ACID. 


This  acid,  which  has  long  been  known,  attaches  to  the  ethy- 
lene  derivatives.  Oxide  of  ethylene  unites  directly  with  sodium 
acid-sulphite  (bisulphite),  forming  sodium  isethionate. 

C*H*.0     +     N^>SO'  =    C»H*<so.Na 
Sodium  Isetliionate. 

The  same  salt  is  formed  when  ethylene  chlorhydrate  is  heated 
with  neutral  sodium  sulphite. 

+     NaCl 


Isethionic  acid  may  also  be  obtained  by  passing  the  vapor  of 
sulphuric  anhydride  into  cold  absolute  alcohol  or  ether;  the 
liquid  is  then  mixed  with  four  times  its  volume  of  water,  and 
boiled  for  several  hours,  after  which  it  is  neutralized  with 
barium  carbonate.  The  filtered  liquid  contains  barium  isethi- 
onate, which,  when  exactly  decomposed  by  sulphuric  acid,  fur- 
nishes isethionic  acid. 

Isethionic  acid  is  a  sour  liquid  which  cannot  be  entirely 
deprived  of  water  without  decomposition.  Its  salts  are  very 
stable.  It  is  isomeric  with  ethylsulphuric  acid.  Phosphorus 
pentachloride  transforms  it  into  a  chloride. 

+  2PCP  =  C2H*<  +  HC1  +  KC1  +  2POCJ3 


Potassium  isethionate.  Chlorcthylsulphurous 

chloride. 

The  latter  body  is  a  liquid,  boiling  at  120°  ;  it  is  decomposed 
by  the  action  of  water  at  100°,  into  chlorethylsulphurous  acid 
and  hydrochloric  acid. 

+     H2°    =     C2H4  +     HC1 


Chlorethylsulphurous  acid. 

TAURINE. 

C'H'NSO' 

This  important  acid,  whose  existence  in  the  bile  was  dis- 
covered by  Gmelin  in  1824,  is  related  to  isethionic  acid  ;  it  is 
amido-isethionic  acid,  that  is,  it  is  derived  from  the  latter  acid 


PROPYLGLYCOLS  —  GLYCERIN.  529 

by  the  substitution  of  a  group  NH2  for  a  group  OH.  It  may 
be  obtained  by  synthesis  by  the  action  of  ammonia  on  chlor- 
ethylsulphurous  acid  or  on  silver  chlorethylsulphite.  The  fol- 
lowing formulse  indicate  the  relations  between  isethionic  and 
chlorethylsulphurous  acids  and  taurine  : 


Isethiouic  aci«l.  Chlorethylsulphurous  acid.  Taurine. 

Taurine  crystallizes  in  large,  brilliant,  oblique  rhombic  prisms, 
very  soluble  in  boiling  water  and  but  slightly  soluble  in  cold 
water.  When  the  crystals  are  heated  they  melt,  and  decompose 
at  an  elevated  temperature. 

Strecker  has  obtained  an  isomeride  of  taurine  by  heating 
ammonium  isethionate. 

C21I4<s5(NH*)     =        C'H4<SO«,NH*    +     H2° 

Ammonium  isethionate.  Isethionamide. 

PROPYLGLYCOLS. 

C3H6(OH)2 

Normal  propylglycol  (page  522)  has  been  obtained  from 
normal  propylene  bromide  (page  518).  This  bromide  is  mixed 
with  acetic  acid  and  heated  with  silver  acetate  :  propylene  di- 
acetate  is  formed,  C3H6(C2H302)2,  and  separated  by  distillation, 
after  which  it  is  decomposed  by  a  quantity  of  dry  potassium 
hydrate  just  sufficient  to  remove  its  acetic  acid. 

Normal  propylglycol  is  a  colorless,  syrupy  liquid,  boiling  at 
216°,  and  having"  a  density  of  1.0652  at  0°.  It  is  miscible 
with  water  and  alcohol  in  all  proportions.  When  oxidized,  it 
yields  hydracrylic  acid  (Geromont,  Reboul). 

Ordinary  propylglycol  is  prepared  from  ordinary  propylene 
bromide  by  the  same  process  indicated  above.  It  is  a  thick, 
colorless  liquid,  having  a  density  of  1.051  at  0°.  It  boils  at 
188-189°.  When  diluted  with  water  and  mixed  with  plati- 
num black,  it  absorbs  oxygen,  and  is  converted  into  lactic  acid 
(A.  Wurtz) 

GLYCERIN. 

C3H8Q3  = 


Glycerin  was  discovered  by  Scheele  in  1799,  and  studied  by 
Chevreul,  Pelouze,  and  especially  by  Berthelot,  who  demon- 
strated its  character  of  a  triatomic  alcohol. 


45 


530  ELEMENTS    OF    MODERN    CHEMISTRY. 

Pelouze  and  Gelis  realized  the  first  artificial  formation  of  a 
fatty  body  by  passing  hydrochloric  acid  gas  into  a  mixture  of 
butyric  acid  and  glycerin :  butyrin  was  thus  produced. 

Preparation. — Glycerin  is  an  accessory  product  in  the  man- 
ufacture of  lead  plaster.  When  the  preparation  of  that  sub- 
stance is  terminated,  the  water  is  decanted  from  the  lead  soap 
which  separates,  and  hydrogen  sulphide  is  passed  through  the 
liquid  in  order  to  precipitate  as  sulphide  any  traces  of  lead  that 
may  be  dissolved.  It  is  then  filtered  and  evaporated  on  a 
water-bath.  The  glycerin  remains  as  a  colorless,  syrupy  liquid. 

It  is  obtained  in  large  quantities  in  the  arts  as  an  accessory 
product  in  the  manufacture  of  stearin  candles. 

Properties. — Glycerin  is  a  colorless  liquid,  having  a  syrupy 
consistence  and  a  sweet  taste.  Its  denstity  at  15°  is  1.28.  It 
dissolves  in  all  proportions  in  water  and  alcohol,  but  is  almost 
insoluble  in  ether.  When  quickly  heated,  it  distils  between 
275  and  280°  ;  and  it  may  be  readily  distilled  in  a  vacuum. 

Pure  glycerin  is  crystallizable,  and  solidifies  below  0°,  but 
solid  glycerin  melts  only  at  7  or  8°  (Gladstone). 

When  subjected  to  the  action  of  dilute  nitric  acid,  glycerin 
is  converted  into  a  triatomic  acid,  which  is  called  glyceric  acid 
(Debus,  Socoloff). 

C3H803  +  O2  =  H20  -f  C3H604 

Glycerin.  Glyceric  acid. 

When  glycerin  is  poured  drop  by  drop  into  a  mixture  of 
concentrated  nitric  and  sulphuric  acids,  cooled  in  a  vessel  of 
cold  water,  oily  drops  of  trinitroglycerin,  C3H5(0-N02/,  are 
precipitated.  It  is  a  yellowish  oil,  which  explodes  with  great 
violence  by  percussion,  by  heat,  or  sometimes  even  sponta- 
neously. 

On  account  of  this  property,  nitroglycerin  is  employed  as  an 
explosive ;  but  it  is  generally  incorporated  with  inert  matter, 
such  as  finely-divided  silica.  Such  mixtures  are  called  dyna- 
mites. 

When  heated  with  phosphorus  iodide,  P2!4,  glycerin  is  con- 
verted into  allyl  iodide  (Berthelot  and  de  Luca)  (page  478). 

ETHERS   OF   GLYCERIN. 

Glycerin,  C3H5(OH)3,  which  contains  three  groups  OH,  can 
form  three  classes  of  ethers  by  the  substitution  of  one,  two,  or 
three  monobasic  acid  radicals  for  as  many  atoms  of  hydrogen 


ETHERS   OF   GLYCERIN.  531 

in  these  hydroxyl  groups.  If  acetic  acid  be  heated  with 
glycerin,  according  to  the  proportions  of  the  mixture,  three 
different  acetic  ethers  of  glycerin  may  be  obtained,  ethers  which 
Berthelot  has  designated  as  acetins. 

n     (OH  •„,    (O.C2H30 

C2H3O.OH  -f  C3H5  \  OH  =     H20    +   C3H5^  OH 
(  OH  (  OH 

Acetic  acid.         Glycerin.  Monacetin. 

///   roH  ,,,  ro.c2H3o 

2(C2H3O.OH)  +  C3H5  \  OH   =   2H20  +  C3H5  \  O.C2H30 
(OH  (OH 

Diacetin. 


(OH  ,„     (O.C2H30 

\  ' 


3(C2H3O.OH)  +  C3H5  J  OH    *=    3H20  +  C3H5 1  O.C2H30 
(OH  (O.CW) 

Triacetin. 

In  the  same  manner,  by  the  action  of  the  hydracids  upon 
glycerin,  neutral  combinations  are  formed,  analogous  to  the 
chlorides  of  the  radicals  CnH2n+1,  as  well  as  to  the  dichlo- 
ride  of  ethylene  and  to  ethylene  chlorhydrate.  These  com- 
pounds are  formed  by  the  substitution  of  one,  two,  or  three 
atoms  of  chlorine  or  bromine  for  as  many  hydroxyl  groups  in 
glycerin. 

,„  (OH  „,    (Cl 

C3H&    OH    +    HCl      =      C3H5  \  OH  +   H20 

(OH  (OH 

Monochlorhydrin. 
•  n    (OH  ,„     (Cl 

C3H5  ]  OH    +    2HC1     =      C3H5  \  Cl    +   2H20 

(OH  (OH 

Dichlorhydrin. 

Monochlorhydrin  is  a  thick,  colorless  liquid,  soluble  in  water 
and  alcohol,  and  sensibly  soluble  in  ether.  It  boils  at  227°. 

Dichlorhydrin  is  a  neutral,  oily  liquid,  having  a  pronounced, 
ethereal  odor.  It  dissolves  in  ether.  Its  density  is  1.137,  and 
it  boils  at  178°. 

When  dichlorhydrin  is  treated  with  a  concentrated  solution 
of  potassium  hydrate,  the  elements  of  hydrochloric  acid  are 
removed  and  a  body  is  obtained  which  Berthelot  has  named 
epichlorhydrin. 

CH2C1 
C3H5C12(OH)  — HCl   =   C3H5C10   =   CH  .    Q 

CH2 
Dichlorhydrin.  Epichlorhydrin. 


532  ELEMENTS   OF   MODERN   CHEMISTRY. 

Epichlorhydrin  is  a  mobile  liquid,  heavier  than  water,  and 
having  an  agreeable,  ethereal  odor.  Its  taste  is  at  first  sweet, 
afterwards  sharp  and  burning.  It  boils  at  118-119°.  It  is 
soluble  in  all  proportions  in  alcohol  and  ether,  but  not  in  water. 

It  combines  directly  with  hydrochloric  acid,  regenerating 
dichlorhydrin.  When  heated  for  a  long  time  with  water,  it 
combines  with  one  molecule  of  that  liquid,  forming  monochlor- 
hydrin. 

C3H5C10  +  H20  =  C3H5C1(OH)2 

When  dichlorhydrin  is  heated  with  phosphorus  pentachlo- 
ride,  the  last  hydroxyl  group  is  removed,  being  replaced  by 
chlorine  ;  trichlorhydrin  is  thus  obtained. 

rci  rci 

C3H5  \  Cl  +  PC15   =    C3H*  \  Cl  +   POC13  +  HC1' 

(OH  (ci 

Dichlorhydrin.  Trichlorhydrin. 

Berthelot  has  obtained  a  great  number  of  glycerin  ethers  by 
directly  heating  glycerin  with  acids.  When  the  reaction  is 
terminated  (it  is  often  very  slow),  he  saturates  the  excess  of 
acid  with  calcium  hydrate,  and  extracts  the  neutral  fatty  body, 
that  is,  the  ether  of  glycerin,  with  ether. 

NATURAL  FATTY   BODIES. 

The  fats  encountered  in  nature  are  glycerides,  that  is,  ethers 
of  glycerin.  The  memorable  researches  of  Chevreul  have 
shown  that  when  these  fats  are  methodically  treated  with 
different  solvents,  various  immediate  principles  are  separated, 
of  which  the  most  common  are  stearin,  margarin,  and  olein. 

They  are  the  tristearic,  trimargaric,  and  trioleic  ethers  of 
glycerin. 

ro.cl8H35o  ro.c^H^o  ro.cl8H33o 

C3H5  \  O.C^H^O  C3H5  \  O.C17H330  C3H5  \  O.C^H^O 

(  O.C^H^O  (  O.C^H^O  (  O.C18II330 

Stearin.  Margarin.  Olein. 

When  these  glycerin  ethers  are  subjected  to  the  action  of 
alkalies,  lime,  or  oxide  of  lead,  in  presence  of  boiling  water, 
they  are  decomposed,  absorbing  at  the  same  time  the  elements 
of  water :  glycerin  and  the  acid  are  set  free,  and  the  latter 
combines  with  the  base  forming  a  soap  (see  page  534).  Thus, 
when  stearin  is  boiled  with  milk  of  lime,  calcium  stearate  and 
glycerin  are  formed.  When  olein  is  heated  with  water  and 
litharge,  it  yields  lead  oleate  and  glycerin. 

Most  of  the  natural  fats  are  mixtures  of  these  principles 


NATURAL  FATTY  BODIES.  533 

in  various  proportions,  and  to  the  number  we  may  add  tri- 
palmitin. 

Stearin,  margarin,  and  palmitin  are  solids,  olein  is  liquid. 
In  the  fats,  the  solid  principles  predominate ;  the  oils  contain 
a  larger  proportion  of  olein. 

Stearin  is  extracted  from  tallow.  That  substance  is  dissolved 
in  boiling  ether  and  made  to  crystallize.  The  crystals  are 
pressed,  and  the  operation  is  repeated  with  them  many  times 
until  a  substance  is  obtained  which  crystallizes  in  brilliant  little 
scales,  fusible  at  66.5°.  They  are  but  slightly  soluble  in  alco- 
hol and  in  cold  ether,  but  freely  soluble  in  boiling  ether. 

Palmitin  has  been  extracted,  by  the  aid  of  boiling  alcohol, 
from  palm-oil  which  has  previously  been  submitted  to  heavy 
pressure  between  sheets  of  porous  paper.  It  melts  at  60° 
(Heintz). 

Olein  is  the  predominating  principle  of  olive-oil  and  almond- 
oil,  from  which  it  is  difficult  to  obtain  it  in  a  pure  state.  Ber- 
thelot  has  prepared  triolein  artificially  by  heating  glycerin  to 
a  temperature  between  200  and  240°  with  an  excess  of  oleic 
acid.  The  mass  thus  obtained  is  treated  with  lime  and  ether ; 
the  latter  dissolves  the  triolein  and  leaves  calcium  oleate. 
The  ethereal  solution  is  decolorized  with  animal  charcoal  and 
mixed  with  eight  times  its  volume  of  alcohol,  which  precip- 
itates the  triolein.  When  dried  in  a  vacuum,  triolein  is  an  oil 
which  solidifies  at  10°.  Its  density  is  between  0.90  and  0.92. 
It  is  insoluble  in  water,  and  very  slightly  soluble  in  alcohol. 

In  contact  with  mercuric  nitrate  or  with  peroxide  of  nitrogen 
(red  vapors),  olein  is  converted  into  a  crystalline,  solid,  fatty 
body,  fusible  at  32°,  to  which  Boudet  has  given  the  name 
elaidin. 

Fat  Oils  and  Drying  Oils. — The  oils  of  olives,  sweet 
almonds,  rape-seed,  beech-nuts,  etc.,  acquire  an  acrid  taste  and 
a  disagreeable  odor  when  they  are  long  exposed  to  the  air,  but 
they  do  not  solidify.  They  are  called  fat,  or  non-siccative 
oils. 

Olive-oil  is  the  type  of  this  class.  It  is  extracted  by  press- 
ure from  crushed  olives,  and  has  a  greenish-yellow  color ;  its 
taste  is  sweet  and  agreeable  ;  it  is  odorless.  At  a  temperature 
a  few  degrees  above  0°,  it  becomes  a  solid  mass.  When  agitated 
with  mercurous  nitrate,  it  becomes  solid,  the  olein  which  it 
contains  being  transformed  into  elaidin.  It  becomes  rancid  by 
exposure  to  the  air. 

45* 


534  ELEMENTS   OF   MODERN   CHEMISTRY. 

When  other  oils,  such  as  linseed,  walnut,  hemp-seed,  poppy 
and  castor  oils  are  exposed  to  the  air,  they  thicken  and  finally 
are  converted  into  somewhat  elastic,  yellow,  transparent  masses, 
species  of  soft  varnishes.  They  are,  therefore,  called  drying 
oils,  and  are  employed  in  the  preparation  of  paints  and  varnishes. 

The  changes  which  oils  undergo  on  contact  with  the  air  are 
caused  by  an  absorption  of  oxygen,  and  are  accompanied  by  a 
disengagement  of  more  or  less  carbon  dioxide.  Every  one  is 
familiar  with  the  uses  of  the  natural  fatty  bodies  in  the  arts 
and  in  domestic  economy.  Among  the  industrial  applications, 
we  can  only  mention  the  employment  of  tallow  and  palm-oil  in 
the  manufacture  of  candles,  and  certain  other  oils  in  the  fabri- 
cation of  soaps. 

Stearin  Candles. — To  convert  tallow  into  stearin  candles,  it 
is  saponified  by  lime,  that  is,  it  is  first  converted  into  a  lime 
soap,  which  is  then  decomposed  by  sulphuric  acid.  The  latter 
acid  causes  the  fatty  acids  to  separate,  and  they  solidify  on 
cooling.  They  are  strongly  compressed,  first  between  warm, 
and  finally  between  hot  plates,  so  that  the  oleic  acid  is  ex- 
pressed, while  the  fatty  acids  proper  remain.  This  process, 
which  was  invented  by  de  Milly  and  Motard  in  1829,  consists, 
as  may  be  seen,  in  entirely  saponifying  the  tallow  by  lime.  In 
1854,  de  Milly  modified  it  by  considerably  reducing  the  amount 
of  lime,  and  consequently  the  proportion  of  sulphuric  acid 
required.  But  it  is  then  necessary  to  operate  at  higher  tem- 
peratures by  the  aid  of  superheated  steam.  The  operation  is 
conducted  in  closed  vessels,  and  with  2.5  parts  of  lime,  100 
parts  of  tallow  may  be  saponified  at  a  temperature  of  170  or 
180°. 

Palm-oil  may  be  converted  into  candles  by  a  still  more 
simple  process,  which  consists  in  subjecting  it  to  the  action 
of  superheated  steam  at  300°.  It  is  thus  directly  decom- 
posed into  fatty  acids  and  glycerin,  for  the  vapor  of  water, 
at  the  high  temperature  employed,  acts  precisely  as  would  an 
alkali. 

Soaps. — In  the  south  of  Europe,  and  principally  at  Mar- 
seilles, oils  of  inferior  quality  are  used  for  the  manufacture  of 
soap,  and  the  oils  of  sesame  and  earth-nut  have  been  employed 
for  this  purpose  for  some  years.  These  oils  are  saponified  by 
boiling  them  in  large  boilers  with  a  weak  solution  of  caustic 
soda.  The  oil  thus  becomes  pasty,  the  excess  of  oil  making  an 
emulsion  with  the  solution  of  soap  which  is  first  formed. 


SOAP.  535 

More  concentrated  soda  lye  containing  common  salt  is  then 
added,  and  the  saponification  is  finished  by  boiling ;  the  soap, 
which  is  insoluble  in  the  concentrated  lye,  comes  to  the  surface 
of  the  liquid,  and  the  lye  is  then  drawn  off.  When  the  soap 
is  well  made,  the  paste  hardens  on  cooling ;  it  has  a  bluish-gray 
color,  due  to  a  ferruginous  soap  mixed  with  sulphide  of  iron. 
The  iron  and  sulphur  are  derived  from  the  materials  employed, 
crude  caustic  soda  containing  a  small  quantity  of  iron.  If  this 
paste  be  heated  with  about  one-twelfth  its  weight  of  water,  or 
a  very  weak  solution  of  caustic  soda,  it  melts,  and  if  the  mass 
be  allowed  to  stand  undisturbed,  it  will  separate  into  two  por- 
tions, the  lower  and  strongly-colored  layer  containing  the  more 
dense  ferruginous  soap  ;  the  upper  layer  constitutes  white  soap. 
When  the  latter  is  completely  clarified  by  the  deposit  of  the 
ferruginous  soap,  it  is  drawn  off  into  large  moulds,  where  it  solid- 
ifies. White  soap  is  thus  obtained.  If,  on  the  contrary,  mar- 
bled soap  be  desired,  the  paste  is  frequently  agitated  during  the 
cooling.  The  colored  part,  that  is,  the  ferruginous  soap,  thus  be- 
comes diffused  throughout  the  whole  mass,  forming  bluish  veins. 

For  some  years,  large  quantities  of  soap  have  been  prepared 
by  combining  with  caustic  soda  the  oleic  acid  obtained  as  an 
accessory  product  in  the  manufacture  of  stearin  candles. 

Soft  soaps  have  potassa  for  their  base.  They  are  manufac- 
tured from  various  oils,  such  as  hemp,  poppy,  and  linseed  oils, 
which  are  saponified  by  caustic  potassa  lye. 

Saponification. — It  will  have  been  noticed  that  all  of  these 
industrial  operations  have  for  their  object  the  decomposition 
of  neutral  fats  into  fatty  acids,  either  free  or  combined  with 
a  base.  This  decomposition  has  received  the  name  saponifi- 
cation. It  may  be  effected  by  the  action  of  water  and  heat 
alone,  by  the  action  of  a  base,  or  by  the  action  of  a  powerful 
acid,  such  as  sulphuric  acid  (sulphuric  saponification).  In  the 
latter  case,  the  acid  acts  upon  the  glycerin,  forming  a  sulpho- 
glyceric  acid.  Whatever  process  be  employed  to  effect  this 
decomposition,  the  presence  of  water  is  always  necessary,  for 
the  elements  of  that  liquid  combine  directly  with  the  fatty 
body  which  is  decomposed,  as  Chevreul  has  very  well  shown. 
In  this  respect,  the  decomposition  of  palmitin  by  superheated 
steam  may  serve  as  a  type  for  all  reactions  of  this  class. 

( O.C16H310  f  OH 

C3H5  \  O.C16R310  -f     3IPO    =    C3HM  OH     +     3Ci6H31O.OH 

(  O.C«5H310  (  OH 

Palmitin.  Glyceriu.  Palmitic  acid. 


536 


ELEMENTS    OP   MODERN   CHEMISTRY. 


POLYATOMIC  AND  POLYBASIC  ACIDS. 

These  acids  are  related  to  the  polyatomic  alcohols,  just  as 
the  acids  containing  two  atoms  of  oxygen,  and  which  we  have 
already  studied,  are  related  to  the  monatomic  alcohols. 

The  polyatomic  acids  are  classed  in  several  series,  among 
which  we  must  consider  in  a  special  manner  those  which  in- 
clude gly collie  and  oxalic  acids.  As  we  have  already  seen,- 
these  two  acids  are  products  of  the  direct  oxidation  of  glycol. 

Their  homologues  are  related  to  the  superior  glycols. 

GLYCOLS.  ACIDS,  OH2no3.  ACIDS,  Ol^njjo*. 

CH2.0H  CH2.OH  CO.OH 

CH2.0H  CO.OH  CO.OH 

Glycol.  Glycollic  acid.  Oxalic  acid. 
CH2.0H                        CH2.0H  CO.OH 

CH2  CH2  CH2 

OT.OH  CO.OH  CO.OH 

Normal  propylglycol.  Hydracrylic  acid.  Malonic  acid. 

CH3  CH3 


CH.OH 

CH2.0H 

Isopropylglycol. 

CH2.0H 

CH2 

CH2 


CH.OH 

CO.OH 
Lactic  acid  ot  fermentation. 


CO.OH 

CH2 

CH2 


CH2.0H  CO.OH 

Normal  butylglycol.  Succinic  acid. 

The  first  of  the  above  series  is  that  of  glycol  and  the  supe- 
rior glycols.  Among  the  latter,  the  true  homologues  of  glycol 
would  be  those  which  differ  from  the  latter  by  nCH2,  and  of 
which  the  formulae  would  consequently  be  analogous  to  that 
of  normal  propylglycol.  Ordinary  propylglycol,  which  yields 
lactic  acid  by  oxidation,  is  an  isomeride  of  normal  propylglycol. 

The  second  series  is  that  of  glycollic  acid  and  its  homologues. 
They  are  derived  from  the  corresponding  glycols  by  the  sub- 
stitution of  O  for  H2  in  one  group,  CH2.OH  They  conse- 
quently contain  but  one  carboxyl  group,  CO.OH  ;  they  are 
monobasic,  for  the  hydrogen  atom  of  the  last  group  can  be 
replaced  by  a  metal.  It  will  also  be  noticed  that  they  are  at 
the  same  time  acids  and  alcohols, — acids  by  virtue  of  the  carb- 
oxyl, CO.OH,  primary  alcohols  by  virtue  of  the  group  CH2.OH, 
or  secondary  alcohols  by  virtue  of  the  group  CH.OH. 


GLYCOLLIC   ACID.  537 

The  third  series  is  that  of  oxalic  acid  and  its  homologues. 
They  are  derived  from  the  glycols  by  substitution  of  O2  for 
2H'2  in  two  groups,  CH2.OH.  They  consequently  contain  two 
carboxyl  groups,  CO. OH,  and  they  are  dibasic  because  the 
H  of  each  of  these  groups  may  be  replaced  by  an  equivalent 
quantity  of  metal. 

Between  glycollic  and  oxalic  acids  there  exists  a  remarkable 
acid,  because  it  is  at  the  same  time  a  monobasic  acid  and  an 
aldehyde  :  it  is  glyoxylic  acid.  It  contains  C2H203,  one  more 
atom  of  oxygen  than  oxalic  aldehyde,  which  is  called  glyoxal, 
C2H202,  and  two  atoms  of  hydrogen  less  than  glycollic  acid. 
These  relations  of  composition  will  be  clearly  seen  from  the  fol- 
lowing formulae : 

CH2.0H  CHO  CHO  CO.OH 

CO.OH  CO.OH  CHO  CO.OH 

Glycollic  acid.  Glyoxylic  acid.  Glyoxal.  Oxalic  acid. 

Of  all  the  acids  which  make  up  these  series,  we  can  only 
consider  glycollic  and  lactic  acids,  which  are  members  of  the 
first,  and  oxalic  and  succinic  acids,  which  belong  to  the  second. 
Besides  these,  we  will  briefly  describe  the  intermediate  com- 
pounds, glyoxylic  acid  and  glyoxal. 

GLYCOLLIC  ACID. 
C2H*03  =  CH2(OH)-CO.OH 

This  acid  is  formed  by  the  oxidation  of  glycol.  Strecker 
and  Socoloff  discovered  it  in  the  product  of  the  reaction  of 
nitrous  anhydride  upon  glycocol,  or  sugar  of  gelatine  (see  page 
545). 

R.  Hoffmann  and  Kekule  have  shown  that  it  is  produced  by 
the  action  of  an  excess  of  potassium  hydrate  on  monochlor- 
acetic  acid. 

KC2H2C102     -f     KOH    ==    KC1     +     KC2H303 

Potassium  monochloracetate.  Potassium  gly collate. 

When  pure,  this  acid  forms  deliquescent  crystals,  which  are 
very  soluble  in  water.  It  dissolves  also  in  alcohol  arid  in  ether. 
It  has  a  strong  acid  reaction.  When  heated,  it  loses  the  ele- 
ments of  water,  and  is  converted  into  glycollide,  or  glycollic 
anhydride,  C2H202,  or  C4H404. 

C'H'O3  —  H20  =  C2H202 

Glycollic  acid.  Glycollide. 

X* 


538  ELEMENTS   OF    MODERN    CHEMISTRY. 


GLYOXYLIC  ACID  AND   GLYOXAL. 

Glyoxylic  acid  is  formed  by  the  action  of  dilute  nitric  acid 
on  alcohol.  It  may  be  prepared  by  pouring  into  a  tall  jar, 
by  means  of  a  funnel-tube,  alcohol  of  80  per  cent.,  water,  and 
fuming  nitric  acid,  successively,  so  that  the  layers  may  not  mix 
at  once.  The  whole  is  then  left  for  about  a  week  at  a  temp- 
erature of  20°,  so  that  the  three  layers  may  gradually  mix  by 
diifusion.  Gases  are  disengaged,  and  the  product  contains  nitric 
acid,  glyoxylic  and  gly  collie  acids,  several  ethers  and  aldehydes, 
and  notably  glyoxal.  The  liquid  is  distributed  in  flat  plates 
and  evaporated  to  a  syrupy  consistence  on  a  water-bath.  The 
residue  is  exhausted  with  water,  neutralized  with  chalk,  and  fil- 
tered. Alcohol  is  added  to  the  filtered  liquid,  and  precipitates 
glyoxylate  and  glycollate  of  calcium.  The  alcoholic  mother- 
liquor  contains  glyoxal.  The  precipitate  of  calcium  salts  is 
collected  on  a  filter,  pressed,  and  dissolved  in  boiling  water. 
The  solution  being  allowed  to  evaporate  spontaneously,  the  cal- 
cium glyoxylate,  which  is  least  soluble,  is  deposited  first.  Gly- 
oxylic acid  may  be  isolated  by  decomposing  an  aqueous  solution 
of  calcium  glyoxylate  by  oxalic  acid. 

Glyoxylic  acid  is  a  syrupy  and  very  acid  liquid.  Its  consti- 
tution shows  it  to  be  at  the  same  time  an  acid  and  an  aldehyde, 


and  this  double  function  is  expressed  by  the  formula  i 

CO.OH 

Its  solution  reduces  ammoniacal  silver  nitrate.     When  heated 
with  sulphuric  acid  it  disengages  carbon  monoxide. 

Q2JJ2Q3   =   2CQ  H20 


Nascent  hydrogen  converts  it  into  glycollic  acid. 
C'lPO3  -f  H2  =  C2H403 

Glyoxal.  —  This  body  is  formed  at  the  same  time  as  the  pro- 
ducts above  mentioned,  by  the  action  of  weak  nitric  acid  on 
alcohol.  It  is  prepared  from  the  alcoholic  solution  which  sepa- 
rates from  the  calcium  glycollate  and  glyoxylate.  To  this  is 
added  a  concentrated  solution  of  sodium  acid-sulphite,  which 
forms  a  crystalline  combination  with  the  glyoxal.  This  com- 
bination deposits  and  is  collected,  purified  by  recrystallization 
in  water,  and  barium  chloride  is  added  to  its  aqueous  solution. 
A  sulphite  of  glyoxal-barium  is  formed  by  double  decomposi- 
tion, and  deposits  in  crystalline  crusts.  To  its  solution  in  boil- 


LACTIC   AND   PARALACTIC   ACIDS.  539 

ing  water  sulphuric  acid  is  added  in  quantity  exactly  sufficient 
to  precipitate  the  barium  as  sulphate.  The  filtered  liquid  will 
contain  sulphurous  acid  and  glyoxal,  and  the  latter  alone  will 
remain  after  evaporation  on  a  water-bath. 

Glyoxal  is  a  deliquescent,  amorphous  solid,  slightly  colored, 
and  very  soluble  in  water  and  alcohol.  Its  aqueous  solution 
energetically  reduces  ammonio-nitratc  of  silver.  It  combines 
with  the  acid-sulphites,  like  the  other  aldehydes.  Glyoxal  is 
the  aldehyde  corresponding  to  oxalic  acid. 

CHO  CO.OII 

CHO  CO.OH 

Glyoxal.  Oxalic  acid. 

LACTIC   AND   PARALACTIC  ACIDS. 

C3H6Q3  =  CH3-CH(OU)-CO.OH 

Formation  and  Constitution. — Lactic  acid  was  discovered 
by  Scheele  in  sour  milk.  Berzelius  discovered  the  existence  in 
various  liquids  of  the  animal  economy  of  an  acid  which  was  at 
first  believed  to  be  identical  with  that  which  results  from  the 
acid  fermentation  of  milk.  Later,  an  acid  identical  with  the 
latter  was  found  in  various  vegetable  juices,  and  was  recog- 
nized to  be  the  product  of  a  peculiar  fermentation  of  glucose, 
called  the  lactic  fermentation.  It  was  also  discovered  that 
the  lactic  acid  of  fermentation  is  not  identical  with  that  which 
exists  in  the  animal  liquids,  especially  that  liquid  which  im- 
pregnates the  muscular  fibres.  The  latter  acid  is  called  para- 
lactic  acid.  The  nature  of  its  isomerism  with  lactic  acid  has 
been  recently  discovered  by  Wislicenus.  It  is  a  case  of  phys- 
ical isomerism  ;  paralactic  acid  is  optically  active,  and  this 
physical  peculiarity  carries  in  its  train  slight  modifications  in 
chemical  properties ;  these  variations  will  be  indicated  when 
treating  of  the  lactates. 

Independently  of  the  acids  which  have  just  been  mentioned, 
there  is  another  which  was  at  first  named  ethylene-lactic  acid, 
and  which  results  from  the  oxidation  of  normal  propylglycol ; 
its  constitution  is  expressed  by  the  formula 

CH2.0H 

CH2 

CO.OH 

It  is  Tiydracrylic  add;  it  is  also  formed  when  /3-iodopropi- 
onic  acid  is  treated  with  water  and  silver  oxide.  Its  character- 


540  ELEMENTS    OF   MODERN    CHEMISTRY. 

istic  property  is  its  easy  decomposition  into  water  and  acrylic 
acid,  hence  the  name  hydracrylic  (Wislicenus). 

Its  isomeride,  lactic  acid  of  fermentation,  is  formed  by  the 
oxidation  of  ordinary  propylglycol  (A.  Wurtz).  This  fact 
determines  its  constitution,  which  can  also  be  deduced  from 
a  very  interesting  mode  of  formation  discovered  by  Strecker. 
When  a  mixture  of  aldehyde,  hydrocyanic  acid,  and  hydro- 
chloric acid  is  allowed  to  stand  for  some  time,  ammonium  chlo- 
ride and  lactic  acid  are  formed. 

CH3 
?H         +     CNH   4-  HC1  +  2H20  =  NH*C1  +    CH.OH 

CH°  to.OH 

Aldehyde.      Hydrocyanic  Lactic  acid 

acid. 

The  isomerism  of  lactic  and  hydracrylic  acids  may  be  readily 
understood  by  the  aid  of  the  following  formulae : 
CH'.OH  CH3 

CH2  CH.OH 

CO.OH  CO.OH 

Hydracrylic  acid.  Lactic  acid. 

Both  acids  are  monobasic ;  each  contains  the  group  CO.OH, 
which  is  characteristic  of  organic  acids.  The  third  oxygen 
atom  exists  in  alcoholic  hydroxyl,  either  in  the  primary  group 
CH2.OH,  or  in  the  secondary  group  CH.OH. 

The  preceding  formulae  show  that  lactic  acid  has  a  mixed 
function  ;  it  is  at  the  same  time  an  alcohol  and  an  acid.  This 
is  made  evident  in  all  of  its  compounds,  and  it  will  be  sufficient 
to  mention  that  one  molecule  of  lactic  acid  in  its  function  as 
an  acid,  can  react  with  and  etherify  another  molecule  in  its 
function  of  an  alcohol,  the  hydroxyl  of  the  group  CO.OH 
forming  a  molecule  of  water  with  the  hydrogen  of  the  alco- 
holic hydroxyl  in  the  second  molecule  of  the  acid.  The 
dilactic  acid,  lactic  anhydride,  and  lactide  which  are  formed  by 
the  more  or  less  complete  dehydration  of  two  molecules  of 
lactic  acid,  are  veritable  dilactic  ethers.  This  point  has  been 
developed  by  Grimaux. 

Preparation  of  Lactic  Acid.  —  A  mixture  of  3  kilo- 
grammes of  glucose  dissolved  in  13  litres  of  water,  4  kilo- 
grammes of  sour  milk,  100  grammes  of  old  cheese,  and  1.5 
kilogrammes  of  pulverized  chalk,  is  exposed  to  a  temperature 
of  30  or  35°.  At  the  end  of  a  week,  the  whole  solidifies  to 


PARALACTIC   ACID.  541 

a  mass  of  calcium  lactate.  The  salt  is  purified  by  crystal- 
lization, and  is  exactly  decomposed  by  dilute  sulphuric  acid. 
The  calcium  sulphate  is  separated  by  nitration,  and  the  acid 
liquid  is  boiled  and  saturated  with  hydrocarbonate  of  zinc ; 
It  is  then  filtered  and  allowed  to  cool.  The  zinc  lactate  crys- 
tallizes, and  its  solution  being  decomposed  by  hydrogen  sul- 
phide, zinc  sulphide  and  lactic  acid  are  obtained.  The  latter  is 
separated  by  filtration  and  its  solution  concentrated  on  a  water- 
bath. 

Properties. — Lactic  acid  is  a  colorless,  syrupy  liquid,  having 
a  decided  acid  taste.  When  heated,  it  begins  to  lose  water  at 
130°,  and  is  converted,  little  by  little,  into  a  yellow,  amorphous 
mass,  insoluble  in  water,  but  soluble  in  alcohol  and  ether.  This 
body  is  dilactic  acid,  C6H1005. 

2C3H603  =  C6H1005  +  H20 

At  230°,  it  disengages  a  small  quantity  of  carbon  monoxide 
and  carbon  dioxide,  and  a  product  distils  which  often  solidifies 
on  cooling.  It  is  lactide,  or  dilactic  anhydride,  and  is  derived 
directly  from  dilactic  acid. 

C6HioO5    _.     c6H804     +     H20 

Dilactic  acid.  Lactide. 

Lactide  has  been  represented  by  the  more  simple  formula 
C3H*02,  but  L.  Henry  has  shown  by  a  determination  of  vapor 
density  that  the  double  formula  represents  the  true  constitution 
of  this  body.  Grimaux  had  already  arrived  at  the  same  con- 
clusion from  theoretical  considerations. 

Lactide  occurs  in  colorless  crystals,  soluble  in  water  and 
alcohol.  It  possesses  the  property  of  combining  directly  with 
the  elements  of  water,  lactic  acid  being  reformed ;  it  also  com- 
bines with  ammonia,  forming  lactamide. 

Paralactic  Acid. — This  is  the  lactic  acid  which  may  be 
extracted  from  meat.  It  is  also  called  sarcolactic  acid.  It  may 
be  prepared  from  commercial  extract  of  meat ;  this  is  dissolved 
in  4  parts  of  water,  and  the  solution  precipitated  by  8  parts 
of  90  per  cent,  alcohol.  The  alcoholic  solution  is  decanted, 
and  the  residue,  which  is  insoluble  in  alcohol,  is  exhausted  with 
2  parts  of  lukewarm  water,  the  solution  again  being  precip- 
itated by  alcohol.  The  alcoholic  solutions  are  united  and  dis- 
tilled on  a  water-bath.  The  residue  is  rendered  strongly  acid 
by  sulphuric  acid,  and  agitated  with  ether  which  dissolves  the 

46 


542  ELEMENTS    OF    MODERN    CHEMISTRY. 

paralactic  acid  set  free.  The  ethereal  solution  is  evaporated, 
and  the  acid  is  converted  into  the  salt  of  zinc,  which  is  subse- 
quently decomposed  by  hydrogen  sulphide,  as  has  been  indicated 
for  the  preparation  of  ordinary  lactic  acid.  Paralactic  acid  is 
syrupy  like  its  isomeride.  It  turns  the  plane  of  polarized  light 
to  the  right  (Wislicenus).  When  heated,  it  becomes  dehy- 
drated, yielding  lactide. 

According  to  Wislicenus,  extract  of  meat  contains  still  an- 
other paralactic  acid,  isomeric  with  the  preceding,  but  optically 
inactive. 

Lactates  and  Paralactates. — Lactic  acid  is  a  monobasic 
acid;  the  neutral  lactates  contain  R'C3H503,  or  M"(C3H503)2. 
The  most  characteristic  is  zinc  lactate,  Zn(C3H503 /  -f-  3H2O, 
which  is  but  slightly  soluble  in  cold  water,  and  separates  from 
its  boiling  solution  in  brilliant  needles  or  laminae. 

Zinc  paralactate  crystallizes  with  two  molecules  of  water, 
and  is  much  more  soluble  than  the  ordinary  lactate. 

Calcium  lactate,  Ca(C3H503;2  -f  5H20,  crystallizes  in 
rounded  masses,  formed  of  little  needles  grouped  around  a 
common  centre.  Like  all  the  lactates,  it  is  very  soluble  in 
water  and  alcohol.  Its  isomeride,  calcium  paralactate,  is 
deposited  from  boiling  water  with  4  molecules  of  water  of 
crystallization.  According  to  Wislicenus,  this  salt  contains 
2[Ca(C3H503)2]  -f  9H20. 

Ferrous  lactate,  Fe(C3H503)2,  prepared  by  double  decompo- 
sition of  calcium  lactate  and  ferrous  sulphate,  forms  greenish, 
crystalline  crusts,  soluble  in  water.  It  is  employed  in  medicine. 

Lactamide.  C3H7N02. — When  an  alcoholic  solution  of  lac- 
tide  is  treated  with  ammonia  and  the  liquid  is  evaporated, 
crystals  are  obtained  which  are  soluble  in  water  and  alcohol. 
They  constitute  lactamide. 

C6H804  +  2NH3  =  2C3H7N02 

Potassium  hydrate  decomposes  lactamide  into  lactic  acid  and 
ammonia. 

Lactamide  represents  ammonium  lactate  less  the  elements 
of  water. 

CH»  CH3 

CH.OH  —    H2Q    =     CH.OH 

CO.O(NH*)  CO.NH2 

Ammonium  lactate.  Lactamide. 


HYDRACRYLIC   ACID.  543 

HYDRACRYLIC   ACID. 

(ETHYLENELACTIC,  OR  ETHENELACTIC  ACID.) 

C3H603  =  CH2(OH)-CH2-CO.OH 

This  acid  is  formed  by  the  oxidation  of  normal  propylglycol. 
It  is  also  formed  by  the  action  of  water  and  silver  oxide  on 
/2-iodopropionic  acid. 

CH2I-CH2-C02H  +  AgOH*  =  CH2.OH-CH2-CO.OH  -f  Agl 

/3-Iodopropionic  acid.  Hydracrylic  acid. 

The  silver  salt  formed  in  the  latter  reaction  is  converted  into 
the  zinc  salt,  and  the  latter  is  decomposed  by  hydrogen  sul- 
phide. 

Hydracrylic  acid  is  syrupy.  When  heated,  it  breaks  up 
into  acrylic  acid  and  water. 

2       H20 


When  heated  with  hydriodic  acid,  it  is  again  converted  into 
/2-iodopropionic  acid.  Its  sodium  salt,  NaC3H503,  deposits  from 
alcohol  in  crystals  fusible  at  142-143°.  Between  180  and  200°, 
it  loses  water,  and  is  partly  converted  into  sodium  acrylate. 

Zinc  hydracrylate,  Zn(C3H503)2  -f-  H20,  is  characteristic. 
It  forms  large,  very  brilliant  crystals,  soluble  in  about  one  part 
of  water. 

GLYCERIC  ACID. 
C3H6Q*  =  CH2(OH)-CH(OH)—  CO.OH 

This  acid  is  obtained  by  oxidizing  glycerin  with  nitric  acid, 
or  by  treating  it  with  bromine  and  water.  It  is  also  formed 
by  the  spontaneous  decomposition  of  nitroglycerin. 

It  is  prepared  by  introducing  into  a  tall  jar  one  part  of  nitric 
acid  of  specific  gravity  1.5,  and  1  part  of  glycerin  diluted  with 
its  own  volume  of  water.  Care  is  taken  that  the  two  liquids  may 
not  mix,  and  the  whole  is  left  to  itself  for  five  or  six  days.  The 
two  bodies  gradually  mingle  and  react  upon  each  other.  The 
liquid  is  evaporated  on  a  water-bath,  and  the  residue  is  boiled 
with  well-washed  hydrate  of  lead  suspended  in  water,  after 
which  the  solution  of  lead-salt  is  filtered  hot.  Crystals  of  lead 

*  Instead  of  Ag20  +  H20. 


544  ELEMENTS    OF    MODERN    CHEMISTRY. 

glycerate  separate  on  cooling;  they  are  purified,  and  their 
aqueous  solution  when  decomposed  by  hydrogen  sulphide,  fur- 
nishes glyceric  acid. 

Properties. — Grlyceric  acid  is  a  thick,  light-yellow  syrup, 
soluble  in  water  and  alcohol.  Its  reaction  is  acid ;  it  is  mono- 
basic. Hydriodic  acid,  by  the  aid  of  heat,  converts  it  into 
/5-iodopropionic  acid.  Its  relations  with  glycerin  may  be  seen 
in  the  following  formulae : 

CH2.OH  CO.OH 

CH.OH  CH.OH 

CH2.0H  CI12  OH 

Glycerin.  Glyceric  acid. 


Closely  related  to  glycollic  and  lactic  acids  are  two  important 
nitrogenized  bodies,  glycocol  and  alanine.  They  form  part  of 
a  series  which  includes  among  other  bodies  leucine,  a  nitro- 
genized compound  which  plays  a  part  in  the  animal  economy. 

When  a  current  of  nitrous  anhydride  is  passed  into  solutions 
of  glycocol,  alanine,  and  leucine,  nitrogen  is  disengaged,  and 
these  bodies  are  converted  into  glycollic,  lactic,  and  leucic  acids. 
We  then  have  the  following  series : 

C2H403  C2H5N02 

Glycollic  acid.  Glycocol. 

C3H603  C3H7N02 

Lactic  acid.  Alanine. 

Q6JJ12Q3  C6H13N02 

Leucic  acid.  Leucine. 

GLYCOCOL. 
C2H5NO2  =  CH2(NH2)-CO  OH 

This  body  is  related  to  glycollic  acid.  It  was  discovered  by 
Braconnot,  who  obtained  it  by  boiling  gelatin  with  dilute  sul- 
phuric acid  for  a  long  time,  saturating  the  solution  with  barium 
carbonate  and  evaporating  the  filtered  liquid.  Hence  the  name 
sugar  of  gelatin  or  glycocol. 

Cahours  obtained  it  by  the  action  of  ammonia  on  mono- 
chloracetic  acid. 

<?°-°H      +    SNIP    =   WHMJ1  +     ?°'OH 
CH2C1  CH2.NH2 

Monochloracetic  acid.  Glycocol. 

It  is  therefore  amidacetic  or  acetamic  acid. 


ALANINE.  545 

It  is  a  solid  body,  crystallizing  in  oblique  rhombic  prisms, 
fusible  at  170°.  Its  taste  is  sweet.  It  is  soluble  in  water, 
slightly  soluble  in  alcohol,  insoluble  in  ether.  Its  solution  has 
a  feeble  acid  reaction.  Indeed,  glycocol  can  react  with  the 
bases,  forming  compounds ;  when  it  is  digested  for  several  hours 
at  a  temperature  between  80  and  104°  with  silver  oxide,  the 
latter  is  dissolved,  and  the  compound  C2H4AgN02  is  formed. 
On  the  other  hand,  glycocol  will  combine  with  the  acids;  there 
is  a  crystallizable  nitrate  of  glycocol. 

When  nitrous  anhydride  is  passed  into  a  solution  of  glycocol, 
the  latter  is  converted  into  glycollic  acid,  nitrogen  being  at  the 
same  time  disengaged. 

2C2H5N02  +  N203  =  2C2H403  +  H20  +  2N2 

Glycocol.  Glycollic  acid. 


ALANINE. 

C3ITN02  =  CH3-CH(NH2)-CO.OH 

Strecker  made  the  synthesis  of  alanine  by  passing  hydro- 
chloric acid  gas  into  a  mixture  of  aldehyde-ammonia  and  hydro- 
cyanic acid. 

C2H*0  +  CNH  -f  H20  =  C3H7N02 

The  brown  liquid  resulting  from  this  reaction  is  evaporated. 
Alanine  crystallizes  in  hard  needles,  grouped  in  stars  or  tufts. 
It  is  soluble  in  water,  only  slightly  soluble  in  alcohol,  insoluble 
in  ether.  The  aqueous  solution  is  neutral,  and  is  converted 
by  nitrous  anhydride  into  lactic  acid,  with  evolution  of  nitrogen. 

2C3H7N02  +  N203  =  2C3H603  +  H20  +  2N2 

Alanine.  Lactic  acid. 

Alanine  may  be  sublimed  by  cautiously  heating  it.  By  dry 
distillation,  it  breaks  up  into  carbon  dioxide  and  ethylamine. 

C3H7N02  =  CO2  +  C2H5.NH2 

It  is  isomeric  with  lactamide  and  with  an  acid  amide  which 
is  obtained  by  the  action  of  ammonia  on  /9-iodopropionic  acid. 
The  following  formulae  account  for  these  isomerides : 

CH3  CH2.NH2  CH3 

CH.OH  CH2  CH.NH2 

CO.NH2  CO.OH  CO.OH 

Lactamide.  /3-amidopropionic  acid.  Alanine. 

46* 


546  ELEMENTS   OF    MODERN    CHEMISTRY. 

/?-amidopropionic  acid,  which  is  formed  in  the  reaction  just 
indicated,  crystallizes  in  transparent  and  colorless  oblique 
rhombic  prisms.  It  is  very  soluble  in  water  and  but  slightly 
soluble  in  alcohol.  When  cautiously  heated  to  170°,  it  partly 
sublimes  in  needles. 

LEUCINE. 


This  body  was  discovered  by  Proust,  in  1818,  in  old  cheese. 
It  seems  to  be  identical  with  a  substance  obtained  from  cadav- 
eric fat,  and  named  by  Fourcroy  aposepcdine.  It  is  a  product 
of  the  putrefaction  of  animal  matters.  It  is  also  formed  when 
horn,  gelatinous  tissues,  or  albuminous  matters  are  boiled  with 
dilute  sulphuric  acid,  or  fused  with  potassium  hydrate.  In 
these  reactions,  tyrosine,  and  sometimes  glycocol,  is  formed  at 
the  same  time. 

Leucine  exists  already  formed  in  the  economy.  It  is  met 
with  in  the  tissues  of  the  liver,  spleen,  lungs,  pancreas,  and 
in  the  salivary  glands,  etc.  Limpricht  has  formed  it  artifi- 
cially, by  a  process  analogous  to  that  employed  by  Strecker  for 
the  synthesis  of  alanine. 

Preparation.  —  The  best  process  for  the  preparation  of  leu- 
cine,  consists  in  boiling  for  twenty-four  hours  2  parts  of  horn- 
shavings  with  5  parts  of  sulphuric  acid  and  13  parts  of  water, 
care  being  taken  to  replace  the  water  as  it  evaporates.  The 
liquid  is  neutralized  with  milk  of  lime,  the  calcium  sulphate 
separated  by  filtration,  and  a  small  quantity  of  lime  that  re- 
mains in  solution  is  precipitated  by  oxalic  acid.  The  filtered  solu- 
tion, left  to  itself,  first  deposits  tyrosine,  and  the  leucine  remains 
in  the  mother-liquor,  from  which  it  separates  in  crystals  on  spon- 
taneous evaporation.  It  is  finally  crystallized  from  weak  alcohol. 

Properties.  —  Leucine  crystallizes  in  white  plates.     It  dis- 
solves in  27  parts  of  cold  water  and  much  more  abundantly  in 
boiling  water.     It  melts  at  170°,  and  decomposes  at  a  higher 
temperature  into  carbon  dioxide  and  amylamine. 
C'EPNO2  =  CO2  +  C5Hn.NH2 

When  nitrous  anhydride  is  passed  into  a  solution  of  leucine, 
it  is  converted  into  a  homologue  of  lactic  acid,  leucic  acid 
(Strecker). 

2C6H13N02  +  N203  ±=  2C6H1203  -f-  H20  +  2N2 

Leucic  acid. 


OXALIC   ACID.  547 

OXALIC  ACID. 

C2H20*  =  CO(OH)-CO(OH) 

Natural  State  and  Modes  of  Formation. — This  important 
acid  exists  in  many  vegetables.  Wiegleb  and  Scheele  extracted 
it  from  salt  of  sorrel,  which  is  an  acid  oxalate  of  potassium. 

The  process  of  Scheele  has  become  classic.  It  consists  in 
precipitating  a  solution  of  salt  of  sorrel  with  acetate  of  lead, 
and  decomposing  the  precipitated  lead  oxalate  by  hydrogen 
sulphide.  The  great  Swedish  chemist  demonstrated  the  iden- 
tity of  the  acid  thus  formed  and  that  which  Bergman  had 
anteriorly  obtained  by  treating  sugar  with  nitric  acid. 

Oxalic  acid  is  met  with  in  the  animal  economy.  Urine  often 
deposits  little  crystals  of  calcium  oxalate,  which  salt  is  some- 
times deposited  in  the  bladder  and  there  forms  rough  concre- 
tions known  as  mulberry  calculi. 

Oxalic  acid  is  formed  by  the  action  of  nitric  acid  or  fused 
potassium  hydrate  on  a  great  number  of  organic  matters. 

Cyanogen  yields  oxalic  acid  by  its  decomposition  in  contact 
with  water  (page  431). 

We  have  already  studied  the  relations  which  exist  between 
oxalic  acid  and  glycol  (page  524). 

Drechsel  has  recently  made  a  beautiful  synthesis  of  oxalic 
acid.  By  passing  carbon  dioxide  upon  sodium  disseminated  in 
very  dry  quartz  sand  and  heated  to  350°,  he  obtained  sodium 
oxalate. 

2C02  +  Na2  =  Na2C204 

Sodium  oxalate. 

Preparation. — Oxalic  acid  is  prepared  in  the  arts  by  two 
processes.  One  consists  in  the  oxidation  of  molasses  of  an 
inferior  quality  by  nitric  acid.  The  operation  gives  rise  to  an 
abundant  disengagement  of  nitrous  vapors  and  carbon  dioxide. 
It  is  conducted  in  leaden  boilers  that  are  not  attacked  in  pres- 
ence of  a  great  excess  of  oxidizable  organic  matter. 

Another  process  consists  in  the  reaction  of  potassium  hy- 
drate on  saw-dust  at  a  high  temperature.  The  mass  is  ex- 
hausted with  water  which  dissolves  out  potassium  oxalate,  and 
the  solution  is  treated  with  milk  of  lime.  Calcium  oxalate  is 
precipitated  and  potassium  hydrate  is  reformed.  The  precip- 
itated calcium  oxalate  is  decomposed  by  sulphuric  acid,  calcium 
sulphate,  which  is  almost  insoluble,  being  formed,  and  oxalic 


548  ELEMENTS   OF   MODERN   CHEMISTRY. 

acid  remaining  in  solution  in  the  water.  When  the  latter  is 
sufficiently  concentrated,  the  acid  is  deposited  in  crystals.  The 
potassium  hydrate  which  remains  in  the  first  solution  is  evapo- 
rated, and  serves  for  new  operations. 

Properties. — Oxalic  acid  crystallizes  from  its  aqueous  solu- 
tion in  large,  transparent  prisms,  containing  2  molecules  of 
water.  When  exposed  to  the  air,  these  crystals  effloresce,  and 
they  completely  lose  their  water  at  100°  or  in  a  dry  vacuum. 
One  part  of  oxalic  acid  dissolves  in  15.5  parts  of  water  at  10°. 
It  is  also  very  soluble  in  alcohol. 

It  melts  in  its  water  of  crystallization  at  98°;  at  132°  it 
begins  to  disengage  gases,  and  between  155  and  160°  it  breaks 
up  into  water,  carbon  monoxide,  carbon  dioxide,  and  formic 
acid. 

C2H20*  =  CO2  -f-  CH202 
C2H204  =  CO2  -f  CO  +  H20 

At  the  same  time,  a  portion  of  the  dry  acid  escapes  decompo- 
sition and  sublimes. 

When  oxalic  acid  is  heated  with  sulphuric  acid,  it  is  de- 
composed into  carbon  monoxide,  carbon  dioxide,  and  water, 
according  to  the  equation  given  above. 

Certain  chlorides  are  reduced  by  ebullition  with  a  solution 
of  oxalic  acid  :  hydrochloric  acid  is  formed,  and  carbon  dioxide 
is  disengaged.  Under  these  circumstances,  auric  chloride  de- 
posits metallic  gold  ;  mercuric  chloride  is  reduced  to  mercurous 
chloride. 

Oxalic  acid  is  a  violent  poison.  In  doses  of  8,  12,  to  20 
grammes,  it  produces  poisonous  effects  which  may  prove  fatal. 
It  acts  upon  the  heart,  retarding  its  movements,  and  upon  the 
nerve  centres,  of  which  it  rapidly  depresses  the  functions. 

If  a  solution  of  oxalic  acid,  or  better,  ammonium  oxalate, 
be  added  to  a  solution  of  calcium  chloride,  a  white  precipitate 
of  calcium  oxalate  is  formed.  This  precipitate  is  formed  even 
in  very  dilute  solutions.  If  a  small  quantity  of  silver  oxalate 
be  heated  in  a  small  test-tube,  the  salt  decomposes  suddenly 
with  a  slight  explosion,  leaving  a  gray  powder  of  metallic 
silver,  part  of  which  is  violently  projected  from  the  tube. 

Ag2C20*  =  2C02  -f  Ag2 

Silver  oxalate. 

These  reactions  characterize  oxalic  acid. 

Oxalates. — Oxalic  acid  is  dibasic.     Its  two  atoms  of  hydro- 


OXAMIDE.  549 

gen  may  be  replaced  by  two  atoms  of  a  univalent  metal,  or  by 
one  atom  of  a  bivalent.  Acid  oxalates  and  neutral  oxalates 
are  known. 

Potassium  Acid  Oxalate,  KHC20*  +  H20.— This  salt  con- 
stitutes the  greater  part  of  the  salt  of  sorrel  of  commerce.  It 
is  extracted  from  the  juice  of  various  kinds  of  Rumex  and 
Oxalis,  the  juice  of  which  is  clarified  with  clay  and  then 
evaporated  to  crystallization.  It  is  but  slightly  soluble  in 
water. 

If  a  concentrated  solution  of  oxalic  acid  be  agitated  with  a 
solution  of  potassium  neutral  oxalate,  a  precipitate  of  potassium 
acid  oxalate  will  be  formed. 

If  a  concentrated  solution  of  oxalic  acid  be  agitated  with 
a  solution  of  potassium  acid  oxalate,  a  white  precipitate  of 
potassium  quadroxalate,  a  combination  of  the  acid  salt  and 
oxalic  acid,  will  be  deposited.  It  contains  C2H20*  -f  KHC204 
-f  2H20. 

Neutral  Potassium  Oxalate,  K2C20*  -f  IPO,  is  obtained 
by  neutralizing  a  solution  of  the  acid  salt  with  potassium  car- 
bonate and  evaporating.  It  crystallizes  in  oblique  rhombic 
prisms,  very  soluble  in  water. 

Ammonium  Oxalate,  (NH4;2C2O  +  H20,  which  is  fre- 
quently used  as  a  reagent,  is  prepared  by  neutralizing  oxalic 
acid  with  ammonia.  The  concentrated  solution  deposits  color- 
less crystals  belonging  to  the  type  of  the  right  rhombic  prism. 
There  is  also  an  acid  oxalate  of  ammonia.  (NH4)HC204. 

Ethyl  Oxalate,  or  Oxalic  Ether,  (C2H5/C204.— This  ether 
may  be  prepared  by  distilling  a  mixture  of  1  part  of  potassium 
acid  oxalate,  1  part  of  alcohol,  and  2  parts  of  concentrated 
sulphuric  acid.  The  addition  of  water  to  the  distilled  liquid 
causes  the  separation  of  an  oily  layer  which  sinks  and  is  de- 
canted. It  is  washed  with  a  solution  of  an  alkaline  carbonate, 
and  distilled,  only  that  portion  being  retained  which  passes 
above  180°.  Oxalic  ether  is  a  colorless  liquid,  heavier  than 
water,  and  having  an  aromatic  odor.  It  boils  at  186°. 

OXAMIDE. 

C202(NH2)2 

If  solution  of  ammonia  be  added  to  ethyl  oxalate,  the  latter 
immediately  solidifies  to  a  white  mass  formed  of  a  crystalline 
powder.  This  is  oxamide. 


550  ELEMENTS   OF   MODERN   CHEMISTRY. 


NH2 
Ethyl  oxalate.  Oxamide. 

Oxamide  is  also  formed  by  the  dry  distillation  of  ammonium 
oxalate. 

NH*.O^p202       r202^NH2 
NHM)^0  °  \NH2      +     2I1  - 

The  latter  reaction,  studied  in  1830  by  Dumas,  led  to  the 
discovery  of  the  amides. 

Oxamide  is  a  white,  crystalline  powder,  very  slightly  soluble 
in  cold  water,  insoluble  in  alcohol,  somewhat  soluble  in  boiling 
water,  from  which  it  is  deposited  on  cooling.  Like  all  of  the 
amides,  it  is  decomposed  by  boiling  potassium  hydrate,  am- 
monia being  disengaged  and  potassium  oxalate  formed. 

Oxamic  Acid.  —  This  body  is  formed  when  ammonium  acid 
oxalate  is  heated  to  between  220  and  238°  (Balard). 

NHHo>C2°2  -   C2°2<m"2   +    H2° 

Ammonium  acid  oxalate.        Oxamic  acid. 

It  is  a  yellowish,  grainy  powder  which  boiling  water  again 
converts  into  ammonium  acid  oxalate  by  the  direct  addition  of 
one  molecule  of  water. 

The  following  formulae  express  clearly  the  relations  existing 
between  oxalic  acid,  oxainic  acid,  and  oxamide  : 


Oxalic  acid.  Oxamic  acid.  Oxamide. 

SUCCINIC   ACID. 

=  CO.OH-CH2-CI12-CO.OH 


This  acid,  which  was  first  obtained  by  the  distillation  of 
amber,  is  one  of  the  products  of  oxidation  by  nitric  acid  of  the 
complex  fatty  acids,  such  as  palmitic  and  stearic  acids.  It  is 
also  formed  by  the  fermentation  of  calcium  malate  and  by  the 
reduction  of  malic  and  tartaric  acids  by  hydriodic  acid. 

Maxwell  Simpson  obtained  it  synthetically  by  decomposing 
ethylene  dicyanide  with  potassium  hydrate. 


=  f.    2NH3 

CH2-CN  CH2-CO.OH 

Ethylene  dicyanide.  Succinic  acid. 

In  this  reaction  the  nitrogen  of  each  cyanogen  group  unites 


SUCCINIC    ACID.  551 

with  H3,  and  is  replaced  by  02H  =  2(H20)  —  H2.  Succinic 
acid  then  contains  two  groups  C02H,  combined  with  ethylene. 
It  is  dibasic. 

Preparation.  —  Succinic  acid  may  be  prepared  either  by  the 
dry  distillation  of  amber  and  purifying  the  solid  product  of 
this  distillation,  or  by  exposing  for  some  time  calcium  malate 
mixed  with  a  small  quantity  of  white  cheese  to  a  temperature 
of  30  or  40°.  By  a  sort  of  fermentation  the  malate  is  then 
converted  into  succinate,  and  the  calcium  succinate,  being  de- 
composed by  dilute  sulphuric  acid,  yields  calcium  sulphate, 
which  is  separated  by  nitration,  arid  a  solution  of  succinic  acid 
which  crystallizes  after  concentration. 

Properties.  —  Succinic  acid  forms  large,  colorless  crystals,  un- 
altered by  the  air,  and  fusible  at  180°.  At  235°  it  boils  and 
breaks  up  into  succinic  anhydride  and  water. 

C4H6Q4        =         C4JJ4Q3        _|_         JJ2Q 
Succinic  acid.        Succinic  anhydride. 

It  is  quite  soluble  in  water,  less  so  in  alcohol,  and  almost  in- 
soluble in  ether. 

When  subjected  to  dry  distillation,  it  loses  one  molecule  of 
water,  and  is  converted  into  succinic  anhydride,  C4H403,  which 
forms  a  white,  crystalline  mass.  The  latter  body  is  converted 
by  phosphorus  pentachloride  into  succinyl  chloride,  C4H402C12. 


?H°-co>o   +   POP    .  POO.   + 

CH2-CCT  CHM30CI 

Succinic  anhydride.  Sxiccinyl  chloride. 

Kekule  has  obtained  monobromo-succinic  and  dibromo-suc- 
cinic acids  by  heating  moistened  succinic  acid  with  bromine  in 
sealed  tubes. 

Monobromo-succinic  acid  is  converted  into  malic  acid  when 
treated  with  water  and  silver  oxide. 


+     AgOH    -    C*H»(OH)<  +     AgBr 

Monobromo-succinic  acid.  Malic  acid. 

Under  the  same  circumstances,  dibromo-succinic  acid  is  con- 
verted into  tartaric  acid. 


+     2AgOH    =    WW(OH)*<  +     2AgBr 

Dibromo-succinic  acid.  Tartaric  acid. 

These  reactions,  which  were  discovered  by  Kekule.  establish 
very  close  relations  between  succinic,  malic,  and  tartaric  acids. 


552  ELEMENTS   OF   MODERN   CHEMISTRY. 

C4H604  succinic  acid. 
OH605  malic  acid. 
OH606  tartaric  acid. 

The  following  formulae  express  the  constitutions  of  these 
acids : 

CH2-CO.OH 

CH'-CO.OH 

CH(OH)-CO.OH 

iH'-CO.OH 

CH(OH)-CO.OH 

CH(OH)-CO.OH 

Malic  acid  is  oxysuccinic  acid,  and  tartaric  acid  is  dioxysuc- 
cinic  acid.  By  reducing  agents,  the  latter  acids  can  be  con- 
verted into  succinic  acid.  When  either  of  them  is  heated  with 
a  large  excess  of  hydriodic  acid,  water  is  formed,  iodine  is  de- 
posited, and  the  liquid  will  be  found  to  contain  succinic  acid 
(Schmitt  and  Dessaignes). 

MALIC    ACID. 
OETOs  =  CO.OH-CH2-CH(OH)-CO.OH 

This  acid,  which  exists  in  a  number  of  vegetables,  was  ex- 
tracted by  Scheele  from  apple-juice.  It  is  generally  prepared 
from  the  berries  of  the  mountain-ash,  gathered  before  their 
complete  maturity ;  they  are  strongly  pressed,  and  the  juice  is 
boiled,  filtered,  and  neutralized  with  milk  of  lime  at  the  ordi- 
nary temperature.  Calcium  malate  is  deposited,  and  this  is 
converted  into  the  acid  malate  by  dissolving  it  in  boiling  water 
acidulated  with  nitric  acid.  The  calcium  acid  malate  may  be 
readily  purified  by  crystallization,  after  which  it  is  converted 
into  malate  of  lead  by  double  decomposition  with  lead  acetate. 
The  lead  salt  is  suspended  in  pure  water  and  decomposed  by 
hydrogen  sulphide ;  the  solution  of  malic  acid  is  then  filtered 
and  evaporated  (Liebig). 

Properties. — Malic  acid  crystallizes  in  little  needles  grouped 
in  rounded  grains.  These  deliquesce  when  exposed  to  the  air. 

The  aqueous  solution  of  malic  acid  has  a  marked  acid  taste. 
When  long  kept,  it  becomes  filled  with  vegetations.  It  de- 
viates the  plane  of  polarization  to  the  left.  However,  there  is 
an  inactive  malic  acid  which  has  no  effect  on  polarized  light 


ASPARAGIN.  553 

(Pasteur).     Solution  of  malic  acid  does  not  produce  a  cloud  in 
lime-water,  neither  in  the  cold,  nor  on  boiling. 

When  malic  acid  is  heated,  it  begins  to  lose  water  at  130°, 
and  between  150  and  200°  is  converted  into  two  acids  which 
are  isomeric  with  each  other,  and  are  known  as  maleic  and 
fumaric  acids. 

C4H605  C4H404  +  H20 

Malic  acid.  Maleic  and  fumaric  acids. 

By  the  action  of  potassium  hydrate  at  about  150°,  malic 
acid  is  decomposed  into  oxalic  and  acetic  acids. 

C4H6O    +  H2O    =     C2H2O4     +     C2H402     +     H2 

Malic  acid.  Oxalic  acid.  Acetic  acid. 


ASPARAGIN  AND  ASPARTIC  ACID. 

Succinic  and  malic  acids  present  simple  and  remarkable  rela- 
tions with  two  nitrogenized  bodies  which  have  long  been  known  ; 
they  are  asparagin  and  aspartic  acids. 

The  latter  body  is  amidosuccinic  acid,  and  bears  the  same 
relations  to  succinic  acid  that  glycocol  (amido-acetic  acid)  bears 
to  acetic  acid.  On  the  other  hand,  its  relations  to  malic  acid 
are  analogous  to  those  of  glycocol  to  glycollic  acid. 

CH3  Cff'.OH  CH2.NH2 

CO.OH  CO.OH  CO.OH 

Acetic  acid.  Glycullic  acid.  Glycocol. 

CH2-CO.OH  CO(OH)-CO.OH  CH(NH2)-CO.OH 

CH2-CO.OH  C II2 -CO.OH  CH2-CO.OH 

Succinic  acid.  Malic  acid.  Aspartic  or  amidosuccinic  acid. 

Asparagin  is  the  monamide  of  aspartic  or  amidosuccinic  acid  ; 
it  is  isomeric  with  the  diamide  of  malic  acid. 

CH(NH2)-CO.NII2  CH.OH-CO.NH2 

CH2-CO.OH  CH2-CO.NH2 

Asparagin.  Malamide. 

Asparagin,  C4H8N203. — This  body  exists  naturally  in  aspa- 
ragus, black  salsify,  the  roots  of  marsh-mallow,  licorice  wood, 
and  in  the  buds  of  cereals,  peas,  vetches,  and  beans  before  they 
flower.  To  extract  it  from  these  vegetables,  they  are  expressed 
while  fresh,  and  the  juice  is  clarified  and  concentrated.  The 
asparagin  is  deposited  in  colorless  crystals.  It  is  only  slightly 
soluble  in  cold  water  and  alcohol,  but  is  more  soluble  in  hot 
water.  It  forms  combinations  with  both  bases  and  acids. 
Y  47 


554  ELEMENTS   OF   MODERN   CHEMISTRY. 

When  boiled  with  these  agents,  it  loses  ammonia  and  is  con- 
verted into  aspartic  acid. 

C4H8N203     -f     H20    =    NH3    =    C4H7N04 

Asparagin.  Aspartic  acid. 

Aspartic  Acid,  C4H7N04,  forms  rhombic  crystals,  slightly 
soluble  in  cold,  and  more  soluble  in  hot  water.  Like  glycocol, 
aspartic  acid  can  form  compounds  with  both  acids  and  bases. 


TARTARIC  ACID. 

C*H606  =  CO.OH-CH(OH)-CH(OH)-CO.OH 

This  important  acid  was  discovered  by  Scheele  in  the  tartar, 
or  argol,  which  is  deposited  in  casks  in  which  wine  is  kept. 
It  is  pTepared  from  purified  tartar,  called  cream  of  tartar,  which 
is  acid  tartrate  of  potassium. 

Preparation. — The  salt  is  dissolved  in  boiling  water,  and 
chalk  is  added  until  all  effervescence,  due  to  the  disengage- 
ment of  carbon  dioxide,  ceases.  Insoluble  calcium  tartrate  is 
deposited,  and  potassium  neutral  tartrate  remains  in  solution. 
The  calcium  tartrate  is  collected  on  a  filter,  and  the  filtrate  is 
precipitated  by  calcium  chloride.  A  new  portion  of  insoluble 
calcium  tartrate  is  thus  obtained,  and  is  washed  and  united  with 
the  first  portion.  This  salt  is  then  suspended  in  water  and 
exactly  decomposed  by  dilute  sulphuric  acid ;  calcium  sulphate 
is  precipitated,  and  separated  by  filtration,  and  the  filtered 
liquid,  when  sufficiently  concentrated  and  allowed  to  evaporate 
in  a  warm  place,  deposits  crystals  of  tartaric  acid. 

Properties. — Tartaric  acid  crystallizes  in  large,  oblique  rhom- 
bic prisms,  which  often  present  hemihedral  facettes.  They  are 
unaltered  by  the  air,  and  dissolve  in  about  half  their  weight 
of  cold  water  and  still  more  abundantly  in  boiling  water. 
They  dissolve  also  in  alcohol,  but  not  in  ether. 

The  aqueous  solution  of  tartaric  acid  turns  the  plane  of 
polarization  to  the  right.  It  forms  white  precipitates  in  lime- 
water  and  baryta-water,  but  an  excess  of  the  acid  redissolves 
these  precipitates. 

If  an  excess  of  tartaric  acid  be  added  to  a  solution  of  cupric 
sulphate,  the  liquid  may  be  saturated  with  potassium  hydrate, 
but  no  precipitation  of  cupric  hydrate  will  take  place.  The 
liquid  will  remain  transparent  and  will  assume  a  beautiful 
dark-blue  color ;  it  is  called  cupro-potassic  solution.  In  the 


TARTARIC   ACID.  555 

same  manner,  ferric  chloride,  to  which  tartaric  acid  has  been 
added,  is  not  precipitated  by  an  excess  of  potassium  hydrate. 

When  tartaric  acid  is  fused  with  potassium  hydrate,  it  is 
decomposed  into  acetic  and  oxalic  acids. 

2         C2H204 


Action  of  Heat  on  Tartaric  Acid.  —  1.  Tartaric  acid  fuses 
between  170  and  180°,  and  when  the  action  ot  the  heat  is  not 
prolonged,  it  is  converted  into  an  isomeric  acid,  called  meta- 
tartaric. 

2.  If  the  acid  be  maintained  for  some  time  in  fusion,  it 
loses  water  and  is  converted  into  ditartaric  acid. 

2C*H606  ±=  C8H100U  -f-  H20 

Ditartaric  acid. 

3.  When  15  or  20  grammes  of  tartaric  acid  are  suddenly 
heated  over  a  naked  fire  for  four  or  five  minutes,  the  mass 
swells  up  and  a  deliquescent,  yellow,  spongy  mass  is  obtained, 
which  constitutes  what  is  called  tartaric  anhydride. 

C4H6Q6    =     C4H405     +     H2O 
Tartaric  anhydride. 

When  heated  for  some  time  to  150°  in  a  hot-air  oven,  tar- 
taric anhydride  becomes  insoluble. 

4.  When  tartaric  acid  is  distilled  by  heating  it  gradually  in 
a  retort  to  300°,  it  is  transformed  into  two  pyrogenous  acids, 
pyruvic  and  pyrotartaric  acids. 

OH606  =  C3H403  +  CO2  +  H20 

Pymvic  acid. 

2C4H606  =3  C5H8O  +  3C02  +  2H2O 

Pyrotartaric  acid. 

It  is  seen  that  these  acids,  produced  by  the  action  of  heat 
on  a  complex  organic  acid,  differ  from  the  latter  only  by  the 
elements  of  water  and  carbon  dioxide.  Such  is  the  law  of 
pyrogenous  acids  established  by  Pelouze. 

When  tartaric  acid  is  heated  to  1*70°,  in  sealed  tubes,  with 
water,  it  undergoes  a  remarkable  modification  :  it  is  converted 
into  paratartaric  acid  and  inactive  tartaric  acid  ;  the  latter  is  so 
named  because  it  is  without  action  on  polarized  light,  and 
cannot  be  broken  up,  as  can  paratartaric  acid,  into  a  dextrogy- 
rate and  a  levogyrate  acid  (Jungfleisch). 

Action  of  Nitric  Acid  upon  Tartaric  Acid.  —  Very  con- 
centrated nitric  acid  converts  tartaric  acid  into  nitrotartarit 


556  ELEMENTS    OF    MODERN    CHEMISTRY. 

add,  C4H4(N02)206  (Dessaignes).  This  body  may  be  obtained 
in  crystals,  but  it  is  not  stable.  Its  aqueous  solution  decom- 
poses between  40  and  50°,  with  a  brisk  effervescence  of  carbon 
dioxide,  and  formation  of  oxalic  acid.  When  the  decompo- 
sition takes  place  below  36°,  a  peculiar,  crystallizable  acid  is 
formed,  which  Dessaignes  has  named  tartronic  acid.  Its  com- 
position corresponds  to  the  formula  C3H405  ==  C3H203(OH)2. 

TARTRATES. 

Tartaric  acid  is  dibasic ;  it  contains  two  hydrogen  atoms 
which  are  replaceable  by  an  equivalent  quantity  of  metal. 
Neutral  tartrates  and  acid  tartrates  are  known. 

II 1  OH*0«  "  I  C*H*06  ?J'  1  CPH*0«,  or  R"C*H*0* 

11 J  ivi   )  ivi  j 

Tartaric  acid.  Acid  tartrates.  Neutral  tartrates. 

Neutral  tartrates  are  known  in  which  one  atom  of  metal  is 
replaced  by  a  monatomic  oxidized  group,  such  as  (SbO)', 
(FeO/,  (BoO)'. 

H  }  C4H4°6     (SbOr  }  C4II4°6  (FeOr  }  C4H4°6  (BoO^'  }  G*™« 

Potassium  Tartar-emetic.         Ferro- potassium  tartrate.          Boro-potassium 

acid  tartrate.  tartrate. 

Potassium  Acid  Tartrate,  or  Cream  of  Tartar,  KHC4H406, 

is  prepared  from  the  crude  tartar  of  wine-casks  by  subjecting 
that  product  to  several  crystallizations  in  boiling  water.  It 
crystallizes  in  right  rhombic  prisms,  very  slightly  soluble  in 
water.  If  a  concentrated  solution  of  tartaric  acid  be  added 
to  a  saturated  solution  of  potassium  chloride,  a  precipitate  of 
potassium  acid-tartrate  will  be  formed  on  agitating  the  liquid. 
Potassium  Neutral  Tartrate,  K2C4H406.— This  salt  is  pre- 
pared by  neutralizing  a  boiling  solution  of  cream  of  tartar 
with  potassium  carbonate.  The  evaporated  solution  deposits 
on  cooling  oblique  rhombic  prisms,  very  soluble  in  water. 

Potassium  and  Sodium  Tartrate,  Nft }  C*H*O«  -h  4H20.-This 
salt,  which  is  much  used  in  medicine,  was  discovered  in  1672 
by  Seignette,  a  pharmacist  of  Rochelle  ;  hence  it  is  often  called 
Rochelle  salt-,  or  Seignette's  salt.  It  is  prepared  by  neutralizing 
a  boiling  solution  of  cream  of  tartar  with  sodium  carbonate,  and 
evaporating  the  solution.  On  cooling,  the  double  tartrate  is 
deposited  in  large,  beautiful  crystals,  eight-sided  right  rhombic 
prisms. 


ANTIMONIO-POTASSIUM   TARTRATE.  557 


ANTIMONIO-POTASSIUM  TARTRATE,  OR  TARTAR- 
EMETIC. 


This  salt  is  prepared  by  boiling  cream  of  tartar  with  water 
and  oxide  of  antimony,  which  dissolves  abundantly  in  tho 
liquid.  After  nitration  and  cooling,  the  salt  is  deposited  in 
crystals  which  are  purified  by  a  second  crystallization. 

Tartar-emetic  crystallizes  in  rhombic  octahedra,  and  the  crys- 
tals, which  contain  one  molecule  of  water  of  crystallization  for 
two  molecules  of  salt,  effloresce  in  dry  air. 

Its  taste  is  astringent  and  nauseating.  It  dissolves  in  14.5 
parts  of  cold  water  and  in  about  two  parts  of  boiling  water. 
It  is  insoluble  in  alcohol. 

When  heated  to  200°  it  loses  the  elements  of  water  and  is 
converted  into  a  double  tartrate  of  antimony  and  potassium,  in 
which  the  trivalent  antimony  replaces  3  atoms  of  hydrogen  in 
the  tartaric  acid. 

C4tP(SbO)'K06  =  OHW'HKO6  +  H2O 

When  heated  to  redness  in  a  small,  covered  crucible,  tartar- 
emetic  leaves  an  alloy  of  potassium  and  antimony,  disseminated 
in  a  mass  of  charcoal.  When  this  mass  is  exposed  to  moist 
air,  it  suddenly  takes  fire  and  explodes,  projecting  brilliant 
sparks. 

The  following  are  the  characteristics  of  a  solution  of  tartar- 
emetic  : 

Hydrogen  sulphide  forms  an  orange  precipitate  of  antimony 
sulphide. 

A  few  drops  of  hydrochloric  acid  cause  the  appearance  of 
a  white  precipitate  of  antimony  oxychloride,  which  disappears 
in  an  excess  of  acid. 

Potassium  hydrate  produces  a  white  precipitate  of  antimony 
oxide,  which  redissolves  in  an  excess  of  alkali. 

A  plate  of  tin  immersed  in  a  solution  of  emetic  precipitates 
metallic  antimony  as  a  black  deposit. 

Tartar-emetic  is  a  much  employed  medicine.  In  large  doses, 
or  smaller  ones  frequently  repeated,  it  is  an  energetic  poison. 

Ferro-Potassium  Tartrate. — This  salt  is  prepared  by  dis- 
solving ferric  hydrate  in  cream  of  tartar,  and  evaporating  the 

47* 


558  ELEMENTS    OF    MODERN    CHEMISTRY. 

solution.     It  forms  brown,  amorphous  scales,  very  soluble  in 
water.     It  is  used  in  medicine. 

Boro-potassium  Tartrate  is  formed  when  boric  acid  is  dis- 
solved in  a  boiling  solution  of  cream  of  tartar.  It  is  an  amor- 
phous salt,  very  soluble  in  water. 

PARATARTARIC   ACID. 

C8H12012  +  2H2O 

This  acid,  which  is  isomeric  with  tartaric  acid,  exists  in  cer- 
tain tartars.  It  was  discovered  in  1822  by  Kestner,  and  has 
been  studied  by  Berzelius  and  by  Pasteur. 

It  crystallizes  in  transparent,  dissymetric  prisms,  which  efflo- 
resce in  the  air,  losing  their  water  of  crystallization.  It  dis- 
solves in  5.7  parts  of  water  at  15°.  Its  solution  does  not 
change  the  plane  of  polarized  light,  but  Pasteur  has  succeeded 
in  separating  it  into  two  other  acids,  both  of  which  are  optically 
active.  One  of  them  turns  the  plane  of  polarization  to  the 
right,  and  is  ordinary  tartaric  acid;  the  other  deflects  it  to  the 
left,  and  is  levo-tartaric  acid.  These  two  acids,  which  are  iso- 
meric with  each  other,  reproduce  paratartaric  acid  when  they 
are  mixed  in  equivalent  proportions.  It  is  somewhat  remark- 
able that  the  mixture  of  their  solutions  is  attended  by  a 
development  of  heat  (Pasteur). 

The  solution  of  paratartaric  acid  precipitates  solutions  of 
sulphate,  nitrate,  and  chloride  of  calcium,  a  character  which 
tartaric  acid  does  not  possess. 

Independently  of  dextro-tartaric  acid,  levo-tartaric  acid,  and 
paratartaric  acid,  there  is  a  fourth  isomeride,  which  is  inactive 
tartaric  acid.  It  exerts  no  action  on  polarized  light,  and  cannot 
be  separated  into  two  active  acids  (Pasteur). 

Jungfleisch  has  shown  that  these  various  modifications  of  tar- 
taric acid  may  be  produced  at  will  by  the  action  of  a  tempera- 
ture of  about  1*70°  on  a  solution  of  ordinary  tartaric  acid. 

CITRIC   ACID. 


This  acid,  discovered  by  Scheele  in  1784,  is  largely  diffused 
throughout  the  vegetable  kingdom.  It  exists  in  lemons,  oranges, 
limes,  currants,  raspberries,  cherries,  etc. 

It  may  be  advantageously  prepared  from  lemon-juice,  which 


URIC   ACID.  559 

is  allowed  to  stand  until  it  begins  to  ferment,  and  is  then  filtered, 
and  saturated  with  chalk  while  boiling.  The  precipitate  of 
calcium  citrate  is  washed  with  boiling  water,  and  decomposed 
by  a  slight  excess  of  dilute  sulphuric  acid.  The  liquid  sepa- 
rated from  the  calcium  sulphate  yields  crystals  of  citric  acid 
after  concentration. 

This  acid  forms  large,  colorless  crystals,  derived  from  a  right 
rhombic  prism.  It  dissolves  in  three-fourths  its  weight  of 
cold  and  half  its  weight  of  boiling  water. 

When  heated,  it  melts.     At  175°  it  disengages  water,  and 
is  transformed  into  a  pyrogenous  acid,  which  is  identical  with 
the  acomtic  acid  that  may  be  extracted  from  aconite. 
C6H807    =     C6H606    —    H20 

Aconitic  acid. 

If  the  heat  be  increased,  carbon  dioxide  is  disengaged,  inde- 
pendently of  some  accessory  products,  and  oily  streaks  appear 
in  the  neck  of  the  retort,  and  solidify  to  a  crystalline  mass. 
This  product  is  itaconic  acid.  A  portion  of  the  distilled 
product  remains  liquid  ;  it  is  the  anhydride  of  a  third  pyroge- 
nous acid,  isomeric  with  the  preceding,  and  called  citraconic 
acid. 

C6H606     =     C5H6O     +     CO2 

Aconitic  acid.  Itaconic  and 

Citraconic  acids. 

C5H604    =    C5H403     4-     H20 

Citraconic  acid.    Citraconic  anhydride. 

Fused  potassium  hydrate  converts  citric  acid  into  oxalic  and 
acetic  acids. 

C6H807  -f  H2O  =  C2H204  -f  2C2H402 
The  solution  of  citric  acid  has  an  acid  reaction  and  a  very 

sour  taste.     It  does  not  precipitate  lime-water  in  the  cold,  but 

the  solution  becomes  clouded  after  boiling. 
Citric  acid  is  tribasic. 
Magnesium  citrate,  which  is  soluble,  is  employed  in  medi- 

cine ;  it  is  a  purgative,  having  a  sweetish  taste.     Ferric  citrate 

also  is  used  in  medicine. 

URIC  ACID. 


This  body  is  related  to  the  complex  organic  acids  which 
have  just  been  studied.     Among  the  numerous  products  de- 


560  ELEMENTS    OF    MODERN    CHEMISTRY. 

OTT 

rived  from  its  oxidation,  we  may  mention  oxalic  acid,  C202<'rktT, 

OH 
and   an    acid,    C303<Qjj,  which  has  been  called  mesoxalic. 

Uric  acid  itself  seems  to  be  related,  according  to  Baeyer,  to 
tartronic  acid, — one  of  the  products  of  the  transformation  of 
tartaric  acid  (page  556). 

Uric  acid  was  discovered  by  Scheele,  and  its  numerous  meta- 
morphoses were  the  subject  of  a  classic  research  by  Liebig  and 
Wb'hler,  and  have  been  more  recently  studied  by  Baeyer  and 
other  chemists. 

Preparation. — Uric  acid  may  be  extracted  from  the  excre- 
ments of  serpents,  from  guano,  and  from  certain  urinary  cal- 
culi, which  are  almost  entirely  composed  of  it.  These  sub- 
stances are  reduced  to  a  fine  powder,  boiled  with  potassium 
carbonate  and  lime,  and  the  solution  filtered.  The  colored 
solution  of  potassium  urate  is  mixed  with  a  solution  of  ammo- 
nium chloride,  which  produces  a  white  precipitate  of  ammonium 
urate.  This  salt  is  well  washed,  and  treated  with  hydrochloric 
acid,  which  sets  free  uric  acid. 

Uric  acid  may  be  obtained  from  guano  by  boiling  that  sub- 
stance with  an  aqueous  solution  of  borax  (borax  1,  water  120). 
The  boiling  solution  is  filtered,  and  after  cooling  is  precipitated 
by  hydrochloric  acid. 

Properties. — Pure  uric  acid  is  a  light,  white  powder,  which 
has  a  crystalline  aspect  under  the  microscope.  When  slowly 
separated  from  dilute  solutions,  it  sometimes  forms  larger  crys- 
tals, containing  2  molecules  of  water  of  crystallization.  It  is 
often  deposited  from  urine  in  small  rhomboidal  tables  of  a 
brownish-yellow  color. 

Uric  acid  is  insoluble  in  alcohol  and  in  ether.  It  requires 
15,000  parts  of  cold  water,  or  1800  parts  of  boiling  water, 
for  its  solution.  It  dissolves  in  solutions  of  the  alkalies,  form- 
ing neutral  urates  containing  two  atoms  of  the  alkaline  metal. 
It  is  therefore  a  dibasic  acid.  When  carbonic  acid  gas  is 
passed  into  a  solution  of  a  neutral  urate,  an  acid  urate,  which 
is  almost  insoluble,  is  precipitated. 

Hydrochloric  acid  forms  a  thick,  white,  gelatinous  precip- 
itate of  uric  acid  when  added  to  the  solution  of  a  urate. 

When  uric  acid  is  heated  to  160  or  170°  with  an  excess  of 
hydriodic  acid,  it  absorbs  water,  and  is  decomposed  into  glyco- 
col,  carbonic  acid  gas,  and  ammonia  (Strecker). 


METAMORPHOSES   OF   URIC   ACID.  561 


C5H4N403  +  5H20  =  c2H5N02  -f  SCO2  -f  3NH3 

Uric  acid.  Glycocol. 

If  a  small  quantity  of  uric  acid  be  gently  heated  with  nitric 
acid  in  a  porcelain  capsule,  it  is  dissolved  with  a  disengagement 
of  red  vapors,  and  the  solution,  evaporated  at  a  gentle  heat, 
leaves  a  residue  which  assumes  a  purple  color  on  the  addition 
of  a  drop  of  ammonia. 

This  test  is  characteristic  of  uric  acid,  and  permits  the  de- 
tection of  the  least  traces  of  that  substance.  The  purple  body 
formed  is  called  murexide. 


METAMORPHOSES  OF  URIC  ACID. 

Alloxan,  C4H2N204.  —  This  body  is  one  of  the  products  of 
the  oxidation  of  uric  acid  by  nitric  acid  ;  urea  is  formed  at  the 
same  time. 

C5IPN*03  -f  H20  -f  0  =  C4H2N204  -f-  CH4N20 

Uric  acid.  Alloxan.  Urea. 

It  may  be  prepared  by  introducing  uric  acid,  in  successive 
small  quantities,  into  nitric  acid  of  a  density  of  1.41-1.42,  as 
long  as  it  dissolves  producing  red  vapors.  The  alloxan  finally 
separates  in  a  mass  of  delicate  needles  ;  in  about  twenty-four 
hours  they  are  drained  and  dissolved  in  water  at  60  or  65°. 
On  cooling,  the  alloxan  separates  in  voluminous  crystals  con- 
taining 4  molecules  of  water  of  crystallization.  They  efflo- 
resce in  dry  air. 

When  crystallized  from  a  hot  solution,  alloxan  forms  rhombic 
octahedra,  containing  but  a  single  molecule  of  water. 

It  is  very  soluble  in  water,  and  the  solution  is  acid.  By  the 
action  of  alkalies,  baryta-water  for  example,  alloxan  is  con- 
verted into  alloxonic  acid,  which  is  formed  by  the  direct  com- 
bination of  the  elements  of  one  molecule  of  water  with  alloxan. 


|_     JJ2Q     == 
Alloxan.  Alloxanic  acid. 

The  alloxanates  are  decomposed  by  boiling  into  mesoxalic 
acid  and  urea. 

C4H4N205    -f     H20    =     C305H2     +     CH4N20 

Alloxanic  acid.  Mesoxalic  acid.  Urea. 

Mesoxalic  acid,  C303(OH)2  =  CO.OH-CO-CO.OH,  is  a 
dibasic  acid.     According  to  Baeycr,  its  diatomic  radical,  mes- 


562  ELEMENTS   OF   MODERN   CHEMISTRY. 

oxalyl,  exists  in  alloxan  itself,  which  is  mesoxalylurea,  that 
is,  urea  in  which  two  atoms  of  hydrogen  are  replaced  by  the 
diatomic  radical  (C3O3)". 

(CO)")  (CO)" 


H2. 

Urea.  Mesoxalylurea 

(alloxan). 

Parabanic  Acid,  CTWO3.— This  body  is  formed  by  the 
action  of  an  excess  of  nitric  acid  on  alloxan,  which  thus  gives 
up  the  elements  of  carbon  dioxide. 


_|_         Q        = 
Alloxun.  Parabanic  acid. 

Parabanic  acid  forms  thin,  transparent  prisms,  which  are 
very  soluble  in  water.  By  boiling  with  acids,  it  is  transformed 
into  oxalic  acid  and  urea.  Baeyer  regards  it  as  oxalylurea. 

(CO) 
(C 

H2 

When  parabanic  acid  is  heated  with  ammonia,  ammonium 
oxalurate  is  formed,  and  separates  in  fine  needles.  In  this 
case  the  parabanic  acid  is  converted  into  oxaluric  acid  by 
directly  combining  with  the  elements  of  water. 


Parabanic  acid.  Oxaluric  acid. 

It  is  seen  that  oxaluric  acid  is  related  to  parabanic  acid,  as 
alloxanic  acid  is  to  alloxan. 

Alloxantin,  C8H4N4O7.—  This  body  is  produced  by  the  re- 
duction of  alloxan.  When  a  current  of  hydrogen  sulphide  is 
passed  through  a  cold  solution  of  alloxan,  sulphur  separates, 
and  a  crystalline  precipitate  of  alloxantin  soon  forms. 

2C4H2N204  +  H2S  =  C8H4N407  +  H20  +  S 

Alloxan.  Alloxantin. 

Alloxantin  is  also  formed  directly,  at  the  same  time  as 
alloxan,  by  the  action  of  weak  nitric  acid  on  uric  acid.  It 
crystallizes  in  small,  colorless  prisms  containing  3  molecules 
of  water  of  crystallization.  It  is  but  slightly  soluble  in  cold 
water.  Nitric  acid  converts  it  into  alloxan,  and  reducing  agents 
transform  it  into  dialuric  acid. 

Dialuric  Acid,  C4H4N204,  is  the  product  of  the  prolonged 


METAMORPHOSES   OF   URIC   ACID.  563 

action  of  hydrogen  sulphide  on  a  hot  solution  of  alloxan  or 
alloxantin. 

C4H2N204    +     IPS    =     C4H4N204    +     S 

Alloxan.  Dialuric  acid. 

It  is  also  formed  by  the  action  of  sodium  amalgam  on  the 
same  solutions. 

It  crystallizes  in  long  needles,  quite  soluble  in  water ;  these 
crystals  assume  a  red  color  in  the  air,  and  are  gradually  trans- 
formed into  alloxantin. 

When  a  solution  of  alloxan  is  added  to  a  solution  of  dialuric 
acid,  alloxantin  is  formed. 

C4H4N204    +     C*H2N204    =     C8H4N407     +     H20 

Dialuric  acid.  Alloxan.  Alloxantin. 

Baeyer  regards  dialuric  acid  as  tartronyl-urea,  that  is,  urea 
in  which  two  atoms  of  hydrogen  are  replaced  by  the  diatomic 
radical  of  tartronic  acid,  C3H203(OH)2  =  CO.OH-CH(OH)- 
CO.OH. 

(CO)")  (CO)" 

H2  I  NS  (C3H203)" 

H2J  H2 

Urea.  Dialuric  acid 

(tartronyl-urea). 

Purpuric  Acid  and  Murexide.— Scheele  had  already  ob- 
served murexide,  which  Prout  studied  and  described  as  pur- 
purate  of  ammonia.  It  is,  indeed,  the  ammonium  salt  of  a 
nitrogenized  acid,  C8H5N506,  for  which  it  is  convenient  to  pre- 
serve the  name  purpuric  acid  (Beilstein). 

Murexide  is  formed  by  the  action  of  ammonia  on  dry  allox- 
antin heated  to  100°,  or  again,  when  ammonia  or  ammonium 
carbonate  is  added  to  a  hot  solution  of  alloxantin  or  alloxan. 

C8H4N407     +     2NH3    ==     C8H4(NH4)N506     +     H20 

Alloxantin.  Murexide  (ammonium  pnvpurate). 

Murexide  crystallizes  in  quadrangular  prisms,  or  in  tables 
which  are  green  by  reflected  and  red  by  transmitted  light. 
These  crystals,  which  contain  one  molecule  of  water,  present 
the  magnificent  metallic  reflections  shown  by  the  wings  of  can- 
tharides.  They  dissolve  in  water  with  a  rich  purple  color. 

Allantoin,  C4H6N403.— This  body  was  discovered  in  1800, 
by  Vauquelin  and  Buniva,  in  the  allantoic  liquid  of  the  cow, 
that  is,  the  urine  of  the  foetal  calf.  It  occurs  also  in  the  urine 
of  young  calves.  In  1836,  Liebig  and  Wbhler  obtained  it  by 
oxidizing  uric  acid  with  lead  dioxide.  Gorup-Besanez  has 
observed  its  formation  in  the  action  of  ozone  upon  uric  acid. 


564  ELEMENTS   OF   MODERN   CHEMISTRY. 

Grimaux  has  recently  made  the  synthesis  of  allantoin  by 
heating  one  part  of  glyoxylic  acid  with  two  parts  of  urea,  for 
eight  or  ten  hours. 

C2H2O3     -f-     2(CH4N20)     ==     C4H6N4O3     +     2H20 

Glyoxylic  acid.  Urea.  Allantoiu. 

From  this  remarkable  synthesis,  it  appears  that  allantoin  is 
derived  from  two  molecules  of  urea ;  it  is  the  diureide  of  gly- 
oxylic acid. 

Allantoin  may  be  prepared  by  boiling  uric  acid  with  water, 
and  adding  lead  dioxide,  in  small  quantities,  as  long  as  that 
oxide  continues  to  be  converted  into  a  white  powder,  which  is 
lead  carbonate.  The  filtered  liquid,  freed  from  lead  by  hydro- 
gen sulphide,  yields  crystals  of  allantoin  on  evaporation. 

C5H4N4Q3        _|_         JJ2Q         _|_         Q        =        C4H6N403        +         CO2 
Uric  acid.  Allantoin. 

Allantoin  crystallizes  in  brilliant,  colorless  prisms.  It  dis- 
solves in  30  parts  of  boiling  water  and  in  160  parts  of  cold 
water ;  it  is  also  soluble  in  alcohol,  but  is  insoluble  in  ether. 
It  forms  crystallizable  compounds  with  certain  metallic  oxides. 


We  cannot  further  continue  the  study  of  the  numerous  de- 
rivatives of  uric  acid.  This  study  has  already  thrown  great 
light  upon  the  constitution  of  the  acid,  which  Baeyer  regards 
as  derived  from  tartronic  diamide,  that  is,  the  diamide  corre- 
sponding to  tartronic  acid. 


Tartronic  acid.  Tartronic  diamide.        Tartronic  dicyanamido 

(uric  acid). 

Grimaux  has  recently  made  the  synthesis  of  alloxan  ;  all 
of  the  members  of  the  uric  series  can  thus  be  obtained  synthet- 
ically, excepting  uric  acid  itself. 


ALCOHOLS  OF  HIGHER  ATOMICITY. 

One  tetratomic  alcohol  is  known  with  certainty.  It  is  ery- 
thrite,  of  which  de  Luynes  recognized  the  true  nature. 

Glucose,  which  Berthelot  regarded  as  a  hexatomic  alcohol, 
seems  to  fill  a  mixed  function :  it  is  at  the  same  time  an  alde- 
hyde and  a  pentatomic  alcohol. 


ERYTHRITE.  565 

The  best  characterized  hexatomic  alcohol  is  mannite,  a  sweet, 
crystallizable  substance,  which  is  extracted  from  manna.  Glu- 
cose is  related  to  manna,  from  which  it  differs  only  by  two 
atoms  of  hydrogen.  The  constitution  of  mannite  may  be  ex- 
pressed by  the  following  formula : 

C6Hu06  _  c6H8vi(OH)6 

It  results  from  the  experiments  of  Linnemann  that  various 
saccharine  matters,  possessing  the  composition  C6H1206,  fix  H2 
directly  under  the  influence  of  sodium  amalgam  and  water,  and 
are  converted  into  mannite.  The  latter  body  is  characterized 
as  a  hexatomic  alcohol  by  the  property  which  it  possesses  of 
forming  neutral  compounds  with  6  molecules  of  a  monobasic 
acid,  such  as  acetic  acid.  In  other  words,  this  body  contains 
G  hydroxyl  groups,  or  six  atoms  of  hydrogen  capable  of  being 
replaced  by  6  monobasic  acid  radicals. 

ERYTHRITE. 

C4H10O*=  C*H«(OH)* 

This  beautiful  body  was  discovered  in  1849  by  Stenhouse, 
who  found  it  among  the  decomposition  products  of  erythric 
acid  or  erythrin,  a  substance  contained  in  certain  lichens.  In 
1852,  Lamy  obtained  from  an  algae,  the  Protococcus  vulgaris, 
a  substance  which  he  first  named  phycite,  but  which  he  after- 
wards recognized  to  be  identical  with  erythrite. 

Preparation. — De  Luynes  first  extracts  erythrin  from  a 
lichen,  the  Rocella  Montagnei,  and  decomposes  it,  while  still 
moist,  by  slaked  lime  in  closed  vessels  at  a  temperature  of 
150°.  Under  these  conditions,  erythrin  is  decomposed  into 
carbonic  acid  which  is  at  once  taken  up  by  the  lime,  orcin,  and 
erythrite,  which  are  separated  by  crystallization,  the  orcin  being 
deposited  first.  The  erythrite  is  purified  by  washing  it  with 
ether,  which  removes  a  trace  of  orcin. 

Properties. — Erythrite  crystallizes  in  right  square  prisms. 
The  crystals  are  hard,  have  a  feeble,  sweet  taste,  and  are  very 
soluble  in  water,  soluble  in  boiling  absolute  alcohol,  and  insol- 
uble in  ether.  They  melt  at  130°.  Erythrite  reacts  with  the 
acids,  forming  neutral  bodies  analogous  to  the  ethers  (Berthelot). 

When  heated  with  a  concentrated  solution  of  hydriodic  acid, 
it  is  converted  into  secondary  butyl  iodide  (de  Luynes). 
C4Hio04    _|_    YHI    =    c*H9I    -f    4H20    +    3P 

Erythrite.  Secondary  butyl  iodide. 

48 


566  ELEMENTS   OP   MODERN   CHEMISTRY. 

MANNITE. 

C6HKQ6  =  C6H8(OH)« 

This  body,  discovered  by  Prout  in  1806,  exists  in  a  great 
number  of  vegetables.  It  is  the  most  abundant  constituent  of 
manna,  a  substance  which  flows  from  several  species  of  ash, 
either  naturally  or  from  incisions.  It  is  prepared  by  dis- 
solving manna  in  distilled  water,  in  which  the  white  of  an  egg 
has  previously  been  beaten  up.  The  solution  is  boiled  several 
minutes  and  then  filtered  through  a  woollen  cloth  and  allowed 
to  cool.  The  liquid  then  solidities  to  a  mass  of  crystals  which 
are  purified  by  recrystallization  after  treatment  with  animal 
charcoal. 

Mannite  forms  large,  right  rhombic  prisms.  Its  taste  is 
sweet,  and  it  is  soluble  in  water  and  alcohol. 

When  heated  with  a  concentrated  solution  of  hydriodic  acid, 
it  is  reduced  to  a  secondary  hexyl  iodide. 

C6H14Q6       _|_        11HJ       =       Q6JJ13J       _|_        gJpQ       _j_       gp 
Maanite.  /3-secoudary  hexyl  iodide. 

Berthelot  has  described  a  secondary  hexa-stearic  mannite, 
containing  C6H8(C18H33  O2)6. 

But,  by  the  action  of  many  acids  upon  mannite,  compounds 
are  obtained  which  are  not  ethers  of  mannite,  strictly  speak- 
ing, but  of  an  anhydride  of  that  body,  to  which  Berthelot  has 
give  the  name  mannitan. 

C6H14Q6        _        JJ2Q        _±        C6H1205 

Manuite.  Mannitan. 


Mannitan  is  isomeric  with  two  sweet  substances,  quercite,  or 
the  sugar  of  the  glands,  which  was  discovered  in  the  glands  by 
Braconnot,  andpinite,  which  has  been  extracted  by  Berthelot 
from  the  resin  of  the  California  pine. 

Dulcite,  C6H1406,  which  has  been  obtained  from  Madagascar 
manna,  exists  in  certain  plants,  such  as  the  Melampyrnm 
nemorosum,  the  Scrophularia  nodosa,  the  Rhinanthus  crista- 
galli,  and  the  Euonymus  europseus.  It  forms  large,  oblique 
rhombic  prisms,  and  is  less  soluble  in  water  than  mannite ;  it 
is  but  slightly  soluble  in  alcohol.  It  melts  at  188.5°.  It  dis- 
solves in  the  hydracids  without  producing  heat.  Like  its 


SUGARS    AND    STARCHES.  I    .'  56Y 

isomeride,  manna,  it  is  reduced  by  hydriodic  acid  to  a  second- 
ary hexyl  iodide  (G.  Bouchardat). 

Sorbite,  C6HU06,  recently  obtained  by  J.  Boussingault  from 
the  fermented  juice  of  the  mountain-ash,  is  another  isomeride 
of  mannite. 


SUGARS  AND   STARCHES. 

Among  the  more  widely  distributed  products  of  the  vege- 
table kingdom  must  be  included  the  various  kinds  of  sugar, 
starch,  the  gums,  and  the  matter  of  young  vegetable  cells,  or 
cellulose. 

These  compounds  contain  carbon,  hydrogen,  and  oxygen  in 
such  proportions  that  the  oxygen  is  present  in  exactly  sufficient 
quantity  to  form  water  with  the  hydrogen.  Their  composition 
is  then  expressed  by  the  general  formula  Cm(H20)n.  If  all  of 
the  oxygen  and  hydrogen  were  removed  in  the  form  of  water, 
only  carbon  would  remain.  Hence  the  name  hydrates  of  car- 
bon, often  applied  to  this  class  of  bodies. 

Some  of  them  contain  6,  and  the  others  12  atoms  of  carbon, 
and  they  can  be  arranged  in  three  different  classes,  of  which 
the  types  are  glucose,  saccharose,  and  starch. 

Glucose,  or  grape-sugar,  contains  C6H1206. 

Saccharose,  or  cane-sugar,  contains  C12H220U. 

Among  the  important  sugars  of  this  type,  we  may  mention 
lactose,  or  milk-sugar. 

Starch,  or  amylaceous  matter,  has  a  composition  expressed 
by  the  formula  C6H1005.  Its  most  important  isomerides  are 
dextrin,  inulin,  the  gums,  and  cellulose. 

All  of  these  bodies  have  the  power  of  rotating  the  plane  of 
polarized  light,  either  to  the  right  or  to  the  left. 

They  react  with  several  molecules  of  an  acid,  forming  neu- 
tral compounds,  a  property  which  characterizes  them  as  poly- 
atomic alcohols  (Berthelot). 


GLUCOSE. 

C«H1206 

This  important  body,  which  forms  the  solid  and  crystalliza- 
ble  part  of  honey,  exists  in  a  great  number  of  dried  fruits,  on 
the  surface  of  which  it  forms  a  well-known  white  efflorescence. 


568  ELEMENTS    OF    MODERN    CHEMISTRY. 

It  is  also  found  in  the  urine  in  the  disease  known  as  diabetes. 

It  may  be  made  artificially  by  the  action  of  dilute  sulphuric 
acid  on  starch  (KirchhofF),  or  on  cellulose  (Braconnot). 

Preparation.  —  Glucose  is  prepared  in  the  arts  by  the  fol- 
lowing process  : 

6000  litres  of  water  and  42  kilogrammes  of  sulphuric  acid 
are  introduced  into  a  large  wooden  trough,  and  the  liquid  is 
heated  by  jets  of  superheated  steam.  When  it  is  in  full  ebul- 
lition, 2000  kilogrammes  of  starch  suspended  in  2000  litres 
of  warm  water  are  allowed  to  run  in  gradually,  and  in  thirty 
or  forty  minutes  the  saccharification  is  complete.  The  sul- 
phuric acid  is  then  saturated  with  pulverized  chalk,  the  insol- 
uble calcium  sulphate  is  separated,  and  the  liquid  concentrated 
in  boilers  heated  by  steam  until  it  marks  40  or  41°  Bauine. 
It  is  then  allowed  to  crystallize,  and  solidifies  to  an  opaque, 
yellowish,  crystalline  mass,  which  is  glucose. 

The  sulphuric  acid  has  recently  baen  replaced  by  hydrochlo- 
ric acid,  which  produces  a  whiter  product.  The  small  quantity 
of  calcium  chloride  formed  does  not  prevent  the  crystallization 
of  the  glucose. 

Properties.  —  This  body  crystallizes  in  small,  white,  rounded 
masses,  agglomerated  like  cauliflowers.  The  crystals  contain 
one  molecule  of  water  of  crystallization  (C6H12CP  -\-  IPO). 
They  remain  unchanged  in  the  air.  They  melt  when  heated 
on  a  water-bath,  and  losa  their  water  at  100  D.  Anhydrous 
glucose  melts  at  144°. 

Grlucose  dissolves  in  a  little  more  than  its  own  weight  of 
water  at  1*7°.  It  is  three  times  less  soluble  than  cane-sugar, 
and  in  solutions  of  equal  concentration  it  is  three  times  less 
sweet.  It  is  much  less  soluble  in  alcohol  than  in  water. 

The  solution  of  glucose  rotates  the  plane  of  polarization  to 
the  right  ([«]  D  =  56.4°). 

When  glucose  is  heated  to  170°,  it  loses  the  elements  of 
water  and  is  converted  into  a  colorless  mass,  not  very  sweet, 
which  has  received  the  name  glucosan. 


6    =    C6H1005    +     H20 

Glucose.  Glucosan. 

Grlucose  forms  true  compounds  with  the  bases.  There  is  a 
glucosate  of  calcium,  C6H10Ca"06  +  H2O.  It  is  precipitated 
when  alcohol  is  added  to  a  solution  of  calcium  hydrate  in  glu- 
cose. 


GLUCOSE.  569 

These  compounds  are  not  stable. 

If  potassium  hydrate  be  added  to  a  solution  of  glucose  and 
the  liquid  be  heated,  it  first  becomes  yellow,  and  then  rapidly 
assumes  a  deep-brown  color.  The  same  color  is  produced  when 
glucose  is  heated  with  calcium  or  barium  hydrate. 

According  to  Peligot,  there  are  formed  under  these  circum- 
stances two  acids,  which  he  named  glucic  and  melassic  acids. 
Ordinary  or  cane-sugar  does  not  produce  this  reaction,  and  can 
thus  be  distinguished  from  glucose. 

Glucose  reduces  various  metallic  solutions.  If  a  solution  of 
cupric  sulphate  be  poured  into  a  solution  of  glucose,  and  potas- 
sium hydrate  be  added,  no  precipitate  is  formed,  but  the  liquid 
acquires  a  dark-blue  color.  On  heating  it,  a  yellowish  precip- 
itate of  cuprous  hydrate  is  formed. 

This  reaction,  which  was  discovered  by  Troemmer,  is  very 
sensitive,  and  can  be  used  for  the  detection  of  the  smallest 
quantities  of  glucose.  In  making  the  test,  a  cupro-alkaline 
solution  is  employed,  made  by  dissolving  cupric  tartrate  in 
potassium  hydrate  (Barreswill's  solution),  or  by  adding  sodium 
and  potassium  tartrate  and  caustic  soda  to  a  solution  of  cupric 
sulphate  (Fehling's  solution). 

When  a  solution  of  glucose  is  heated  with  bismuth  nitrate 
and  an  excess  of  potassium  hydrate,  a  black  precipitate  of 
reduced  metallic  bismuth  is  formed. 

When  a  solution  of  common  salt  is  added  to  a  solution  of 
glucose  and  the  liquid  is  allowed  to  evaporate  spontaneously, 
crystals  are  deposited  which  constitute  a  definite  compound 
of  the  two  bodies.  They  contain  2(NaCl  -f  2C6H1206)  -f- 
3IPO. 

Glucose  forms  combinations  with  the  acids,  like  mannite,  and 
these  combinations  represent  glucose  in  which  a  certain  num- 
ber of  hydrogen  atoms  are  replaced  by  acid  radicals.  Ber- 
thelot  had  regarded  glucose  as  a  hexatomic  alcohol,  containing 
6  hydroxyl  groups,  but  Colley  has  shown  that  it  is  a  penta- 
tomic  alcohol.  He  has  described  a  compound  produced  by  the 
action  of  acetyl  chloride  on  glucose,  and  which  he  names  aceto- 
chlorhydrose.  It  contains 

(C2H302)* 

On  account  of  the  reducing  properties  of  glucose,  it  may 
be  considered  that  the  oxygen  atom  of  the  group  C6H70  forms 

48* 


570  ELEMENTS   OF   MODERN   CHEMISTRY. 

part  of  an  aldehyde  group  CHO.  Hence  glucose  is  at  the 
same  time  an  aldehyde  and  a  pentatomic  alcohol,  and  its 
constitution  would  be  represented  by  the  formula  CH2.OH- 
CH.OH-CH.OH-CH.OH-CH.OH-CHO. 

The  following  fact  supports  this  view.  When  chlorine  gas 
is  passed  into  a  solution  of  glucose,  the  latter  is  converted  into 
an  acid,  gluconic  acid,  C6H1207,  which  only  differs  from  glucose 
by  containing  one  more  atom  of  oxygen.  This  acid  corre- 
sponds to  gluconic  aldehyde,  and  the  following  formulae  indi- 
cate the  relations  existing  between  the  bodies  just  mentioned  : 

CH2.0H  CH2.C1  CIROH 

(CH.OH)*  (CH.OC2H30)*  (CH.OH)* 

CHO  CHO  CO.OH 

Glucose.  Acetochlorhydrose.  Gluconic  acid. 


LEVULOSE,    OR    UNCRYSTALLIZABLE    FRUIT- 
SUGAR. 


Independently  of  the  glucose  which  effloresces  on  their 
surface  after  desiccation,  many  fruits  contain  another  sugar, 
incapable  of  crystallization,  and  which  strongly  deviates  the 
plane  of  polarization  to  the  left.  It  is  levulose. 

Levulose  exists  in  inverted  sugar  (page  574).  Many  sweet 
fruits  contain  inverted  sugar  ;  among  them  are  grapes,  cherries, 
figs,  gooseberries,  etc. 

It  may  be  extracted  from  inverted  sugar  (a  mixture  of  equal 
proportions  of  glucose  and  levulose).  Dubrunfaut  recommends 
the  following  process  :  10  grammes  of  inverted  sugar,  6  grammes 
of  slaked  lime,  and  100  grammes  of  water  are  intimately  mixed. 
The  mass,  which  is  at  first  liquid,  becomes  pasty  on  agitation, 
and  then  contains  a  solution  of  calcium  glucosate  and  solid  cal- 
cium levulosate.  It  is  strongly  pressed  in  a  cloth  and  the 
compound  of  levulose  and  lime  is  decomposed  by  oxalic  acid. 
The  levulose  remains  in  solution,  and  after  evaporation  forms 
an  uncrystallizable  syrup  which  is  much  sweeter  than  a  solu- 
tion of  glucose. 

Levulose  is  directly  fermentable.     When  heated  to  170°,  it 
loses  the  elements  of  water  and  is  converted  into  levulosan. 
6  =  c6H'°05  _j_  H20 

Levulosan. 


SACCHAROSE.  5*7 1 

Other  sugars  are  known  which  may  be  classed  with  glucose. 
Such  are  the  following : 

1.  Sorbin,  CGH1206,  a  substance  which  crystallizes  in  large, 
transparent  rhombohedra ;  has  been  obtained  from  the  berries 
of  the  mountain-ash  by  Pelouze. 

2.  Inosite,  C6H1206  -f  H20,  a  sugary  matter  extracted  by 
Scherer  in  1850  from  the  muscles,  and  which  has  since  been 
found  in  the  lungs,  kidneys,  spleen,  and  liver  (Cloetta).     In- 
osite is  identical  with  a  substance  that  Vohl  extracted  from 
green  beans,  and  to  which  he  gave  the  name  phaseomannite. 

Inosite  forms  large,  rhombic  tables,  or  transparent,  colorless 
prisms,  having  a  sweet  taste.  The  crystals  effloresce  in  the  air. 
They  are  soluble  in  water,  but  insoluble  in  absolute  alcohol  and 
in  ether.  The  aqueous  solution  is  optically  inactive  ;  it  is  not 
converted  into  glucose  by  the  action  of  dilute  acids ;  it  does 
not  reduce  cupro-potassic  solutions,  nor  will  it  ferment  under 
the  influence  of  yeast. 

SACCHAROSE,  OR   CANE-SUGAR. 

C12H22QH 

Extraction. — Ordinary  sugar,  which  is  universally  diffused  in 
the  vegetable  kingdom,  is  extracted  principally  from  sugar-cane, 
sugar-maple,  and  beet-root.  Fresh  sugar-cane  contains  about 
eighteen  per  cent,  of  sugar :  beet-root  contains  only  about  ten 
per  cent.  (Peligot). 

Certain  sweet  fruits  contain  cane-sugar,  independently  of 
inverted  sugar.  According  to  Buignet,  such  are  apricots, 
peaches,  pine-apples,  lemons,  plums,  and  raspberries. 

We  can  only  briefly  indicate  the  processes  which  are  em- 
ployed for  the  extraction  of  sugar  from  beet-root. 

The  roots  are  washed,  and  reduced  to  pulp  in  a  machine 
provided  with  a  cylinder  armed  with  teeth  and  having  a  rapid 
rotary  motion.  This  pulp  is  then  strongly  pressed  in  woollen 
sacks  by  means  of  a  hydraulic  press,  and  the  juice  is  imme- 
diately transferred  to  large  boilers  having  double  bottoms  and 
heated  by  steam,  and  milk  of  lime  is  added. 

This  operation,  which  is  called  defecation,  is  intended  not 
only  to  separate  certain  substances  which  form  insoluble  com- 
pounds with  the  lime,  but  to  prevent  the  juice  from  becoming 
altered  by  reason  of  its  acidity.  As  the  sugar  itself  dissolves 
a  large  quantity  of  lime,  the  latter  must  be  got  rid  of.  A  cur- 


572  ELEMENTS   OF   MODERN   CHEMISTRY. 

rent  of  carbon  dioxide  is  consequently  passed  into  the  solution, 
and  decomposes  the  saccharate  of  calcium.  Another  process 
of  dechaulage,  recently  devised,  depends  on  the  employment 
of  ammonium  phosphate.  Insoluble  calcium  phosphate  is 
formed,  and  the  ammonia  is  disengaged  on  account  of  the  high 
temperature  at  which  the  operation  is  conducted.  By  this 
process  the  neutralization  is  more  perfect. 

The  liquid  is  then  heated  to  about  95°,  and  filtered  through 
a  layer  of  animal  charcoal  in  grains  ;  it  is  then  concentrated  in 
evaporating-pans  heated  by  steam.  When  the  syrup  marks 
25°  Baume,  it  is  again  filtered  through  animal  charcoal,  and 
the  concentration  is  finished  in  pans  heated  by  steam,  and  in 
which  a  vacuum  is  maintained  during  the  evaporation.  The 
cooking  of  the  syrup  is  thus  carried  on  at  a  temperature  not 
above  75  or  80°,  and  these  conditions  assure  a  fine  quality  of 
product  and  a  good  yield  by  preventing  as  much  as  possible 
the  transformation  of  the  sugar  into  uncrystallizable  sugar. 

When  the  syrup  marks  42  or  43°,  it  is  run  into  cooling- 
pans,  where  it  is  continually  stirred  until  the  sugar  is  depos- 
ited in  small  crystals.  These  are  distributed  in  moulds,  which 
consist  of  terra-cotta  cones  having  a  hole  in  the  summit,  which 
for  the  time  is  closed.  These  cones  are  placed  in  an  oven 
heated  to  25°,  where  the  crystallization  takes  place ;  when  the 
syrup  has  solidified,  the  holes  in  the  cones  are  opened  and  the 
thick  and  colored  mother-liquor  is  allowed  to  drain  out ;  it  con- 
stitutes molasses.  The  loaves  of  sugar,  drained  and  dried,  are 
delivered  to  commerce  as  crude  or  brown  sugar. 

For  some  years  an  apparatus  has  been  used  for  draining 
and  bleaching  of  crude  sugars,  which  consists  of  a  cylindrical 
cage  having  perforated  metallic  walls.  It  is  put  into  rapid 
motion  on  its  axis,  and  the  molasses  is  expelled  through  the 
perforated  walls  by  centrifugal  force.  The  apparatus  is  called 
the  centrifugal  drier. 

Refining  of  Crude  Sugar. — The  crude  sugar  is  crushed, 
sifted,  and  dissolved  in  about  30  per  cent,  its  weight  of  water, 
the  operation  being  conducted  in  a  boiler  heated  by  steam.  5 
per  cent,  of  animal  charcoal  is  then  thrown  into  the  hot  solu- 
tion, and,  after  stirring,  ?  per  cent,  of  beef's,  blood  is  added. 
The  latter  coagulates  in  the  liquid  and  envelops  all  of  the  sus- 
pended particles,  uniting  them  in  a  scum  which  is  easily  re- 
moved. When  the  liquid  becomes  clear,  it  is  drawn  off  and 
filtered.  It  is  then  passed  through  grained  animal  charcoal, 


SACCHAROSE.  573 

which  completely  decolorizes  it.  It  is  concentrated  in  vacuum- 
pans,  from  which  it  is  drawn  into  a  large  copper  vessel  having 
a  double  bottom.  It  is  continually  stirred  until  crystallization 
commences,  after  which  it  is  run  into  moulds,  which  are  then 
placed  in  rooms  heated  to  20°.  After  the  crystallization  is 
completed,  the  syrup  remaining  liquid  is  allowed  to  drain  out. 

At  the  termination  of  the  draining,  a  creamy  mixture  of 
white  clay  and  water  is  poured  on  the  surface  of  the  sugar  in 
each  mould,  and  the  water  of  this  broth  slowly  penetrates  the 
mass  of  sugar,  liquefies  the  syrup  which  remains  between  the 
crystals,  and  carries  it  to  the  lower  part  of  the  mass.  The  clay, 
having  lost  its  water,  contracts,  dries  up,  and  remains  upon  the 
decolorized  sugar  as  a  dry  cake.  It  is  removed,  and  a  syrup 
of  white  sugar  is  run  into  the  whitened  and  porous  loaf  and 
fills  up  all  of  the  spaces  when  it  solidifies  in  the  oven. 

This  operation,  the  object  of  which  is  the  decolorizing  of 
the  sugar-loaves,  is  called  claying.  The  clay  broth  may  be 
replaced  by  syrup  of  white  sugar,  an  operation  which  is  called 
decoloring. 

The  sugar  solidified  in  the  moulds  is  a  compact,  crystalline, 
white  mass,  composed  of  little  grains.  It  may  be  obtained  in 
voluminous  crystals  by  concentrating  the  syrup  until  it  marks 
37°  Baume,  and  then  exposing  it  for  some  days  to  a  tempera- 
ture of  30°  in  copper  vessels,  across  which  threads  are  stretched. 
The  sugar  is  deposited  on  the  threads  in  large  crystals  known 
as  rock-candy. 

Properties  of  Sugar. — Sugar  crystallizes  in  large,  oblique 
rhombic  prisms,  having  hemihedral  facettes.  The  crystals  are 
hard,  anhydrous,  and  unalterable  in  the  air.  It  dissolves  in 
one-third  its  weight  of  cold  water  ;  the  solution  is  thick,  and  is 
known  as  simple  syrup.  Sugar  is  insoluble  in  ether  and  in 
cold  absolute  alcohol.  Boiling  absolute  alcohol  dissolves  a  little 
more  than  one  per  cent. ;  ordinary  alcohol  will  take  up  more. 

The  aqueous  solution  of  sugar  deviates  the  plane  of  polari- 
zation to  the  right,  ([«]D  =  -+-  67°). 

At  160°,  sugar  melts  to  a  thick,  transparent  liquid,  which 
solidifies  to  an  amorphous,  vitreous  mass  on  cooling. 

When  maintained  for  a  long  time  at  a  temperature  of  160 
or  161°,  it  breaks  up  into  glucose  and  levulosan  (Ge"lis). 
C"HB0U       =       C6H1206       +       C6H1005 

Saccharose.  Glucose.  Levulosan. 

Between  190  and  200°  it  loses  the  elements  of  water  and  is 


574  ELEMENTS   OP   MODERN   CHEMISTRY. 

converted  into  a  bitter,  brown,  amorphous  mass,  which  is  desig- 
nated as  caramel. 

Inverted  Sugar.  —  By  the  action  of  dilute  acids,  sugar  is 
converted,  slowly  in  the  cold  and  rapidly  on  boiling,  into  a 
mixture,  in  equal  proportions,  of  two  isomeric  sugars  which 
have  opposite  rotatory  powers  :  they  are  glucose  and  levulose. 
The  mixture  is  called  inverted  sugar. 

CUH«0U     +     H20     =     C6H1206    +     C6H1206 

Saccharose.  Glucose.  Levulose. 

The  same  transformation  is  effected  by  the  soluble  matter 
of  yeast  (Berthelot),  and  also,  according  to  Buignet,  by  the 
action  of  the  peculiar  ferments  which  exist  in  most  fruits. 

Sugar  only  ferments  after  having  first  undergone  this  trans- 
formation into  inverted  sugar  by  the  action  of  the  ferment. 

Nitric  acid  converts  sugar  into  saccharic  acid,  C6H1008,  and 
oxalic  acid. 

Concentrated  sulphuric  acid  carbonizes  it. 

Saccharose  resists  the  action  of  alkalies  better  than  glucose. 
It  forms  with  them  and  with  the  bases  in  general,  definite  com- 
binations known  as  saccharates. 

If  a  mixture  of  sugar  and  slaked  lime  be  triturated  with 
water  and  the  whole  be  thrown  upon  a  filter,  the  liquid  which 
passes  through  will  be  colorless  and  strongly  alkaline.  When 
it  is  heated  to  ebullition,  it  changes  into  a  solid  mass  which 
again  becomes  liquid  on  cooling.  It  is  a  solution  of  saccharate 
of  calcium. 

An  analogous  experiment  may  be  made  with  a  concentrated 
boiling  solution  of  barium  hydrate. 

When  sugar  is  heated  to  150  or  160°  with  barium  hydrate, 
it  yields  lactic  acid.  When  fused  with  potassium  hydrate,  it 
disengages  hydrogen,  and  carbonate,  oxalate,  formate,  acetate, 
and  propionate  of  potassium  are  formed. 

Sugar  forms  a  combination  with  sodium  chloride,  consisting 
of  deliquescent  crystals  which  contain  C12H22Oll.NaCl. 

LACTOSE,   OR  MILK-SUGAR. 

C12H22011 


This  sugar  exists  in  solution  in  the  milk  of  mammals,  and  is 
extracted  from  the  whey  which  remains  after  the  manufacture 
of  cheese.  It  is  only  necessary  to  evaporate  this  liquid  to 
crystallization. 


MALTOSE.  575 

Milk-sugar  occurs  in  commerce  in  cylindrical  masses,  formed 
of  an  agglomeration  of  crystals  around  a  little  stick  which 
serves  as  a  nucleus.  The  crystals  are  colorless,  hard,  and  creak 
when  crushed  by  the  teeth.  They  are  right  rhombic  prisms, 
terminated  by  octahedral  points.  They  contain  one  molecule 
of  water  of  crystallization  which  they  lose  at  about  140°. 
They  dissolve  in  6  parts  of  cold,  and  in  2  parts  of  boiling 
water.  The  solution  turns  the  plane  of  polarization  to  the 
right. 

When  heated  with  nitric  acid,  lactose  yields  certain  acids, 
among  which  is  one  which  is  but  slightly  soluble  in  water,  and 
which  is  called  mucic  acid.  It  contains  C6H1008,  and  is  iso- 
meric  with  saccharic  acid,  which  is  also  produced  by  the  oxi- 
dation of  lactose  by  nitric  acid.  Liebig  found  tartaric  acid 
among  the  products  of  this  oxidation,  and  a  small  quantity  of 
paratartaric  acid  has  also  been  observed  to  be  formed  (Carlet). 
Lastly,  oxalic  acid  is  also  produced. 

When  boiled  with  dilute  sulphuric  acid,  milk-sugar  is  con- 
verted into  glucose  and  another  sugar  isomeric  with  glucose, 
and  to  which  the  name  galactose  has  been  given.  Galactose 
will  undergo  the  alcoholic  fermentation  under  the  influence  of 
yeast.  It  is  crystallizablc,  and  occurs  in  microscopic  crystals 
united  together  in  tufts. 

Milk-sugar  reduces  cupro-alkaline  solutions. 

When  exposed  to  the  air  at  summer  heat,  a  solution  of  lac- 
tose in  presence  of  an  alkaline  salt  or  calcium  carbonate  soon 
undergoes  the  lactic  fermentation  (page  577). 


MALTOSE. 

C12H220U  +  H2O 

This  name  is  given  to  the  crystallizable  sugar  produced  by 
the  action  of  diastase  on  starch.  It  may  be  prepared  by  digest- 
ing starch  paste  at  60°  with  a  solution  of  diastase.  The  solu- 
tion is  precipitated  by  alcohol,  filtered,  the  alcoholic  liquid 
evaporated  to  a  syrupy  consistence,  more  alcohol  added,  and 
the  solution  set  aside  to  crystallize  in  a  bell-jar  over  sulphuric 
acid. 

Maltose  forms  a  crystalline  mass,  composed  of  hard,  white 
needles.  It  loses  its  water  of  crystallization  at  100°.  Its  solu- 
tion turns  the  plane  of  polarization  to  the  right,  [«]D  =  -f- 


576  ELEMENTS   OF   MODERN    CHEMISTRY. 

149.5°.     It  reduces  cupro-potassic  solutions,  and  when  boiled 
with  dilute  acids  is  converted  into  glucose. 


FERMENTATION. 

If  yeast  be  introduced  into  a  tolerably  concentrated  solution 
of  glucose,  and  the  liquid  be  exposed  to  a  temperature  between 
20  and  30°,  bubbles  of  an  incombustible  gas  will  soon  be  dis- 
engaged, and  this  gas  will  produce  a  cloud  in  lime-water.  It 
is  carbon  dioxide. 

After  the  disengagement  of  gas  has  ceased,  a  small  quantity 
of  alcohol  may  be  obtained  by  distilling  the  liquid. 

In  this  experiment,  the  glucose  disappears  ;  it  is  broken  up 
into  alcohol  and  carbon  dioxide.  The  decomposition  is  effected 
by  yeast,  and  is  called  fermentation.  The  sugar  is  the  fer- 
mentable substance  ;  the  yeast  is  the  ferment. 

The  ferment  is  an  organized  matter  which  develops  and  mul- 
tiplies at  the  expense  of  the  glucose.  The  latter,  is  directly  at- 
tacked by  this  being  which  lives  at  its  expense,  and  undergoes  a 
complete  decomposition,  of  which  carbon  dioxide  and  alcohol 
are  the  principal  products.  The  ferment  plays  an  active  part, 
which  was  first  suspected  by  Cagniard-Latour  and  Schwann, 
and  demonstrated  by  Pasteur. 

Alcoholic  Fermentation.  —  The  decomposition  of  glucose 
under  the  influence  of  yeast  constitutes  the  alcoholic  fermenta- 
tion. 

It  is  expressed  in  the  following  equation  : 


6    ==     2C2H60     +    2C02 

Glucose.  Alcohol. 

It  is  shown  by  the  experiments  of  Pasteur,  that  only  94  per 
cent,  of  the  quantity  of  glucose  decomposed  undergoes  the 
change  indicated  by  the  above  formula.  The  remaining  6  per 
cent,  are  employed  :  1,  in  the  formation  of  small  quantities  of 
succinic  acid  and  glycerin  ;  2,  in  the  development  of  new  yeast 
cells. 

Yeast  is  composed  of  a  mass  of  cells  or  ovoid  corpuscles, 
having  a  diameter  of  yj^  of  a  millimetre,  and  arranged  in 
clusters  (Fig.  125).  Their  walls  are  an  elastic  membrane, 
and  their  contents  are  liquid  or  granular.  They  contain  cellu- 
lose, albuminoid  matter,  and  mineral  salts.  When  they  are 


FERMENTATION.  577 

introduced  into  a  substance  which  contains  the  materials  neces- 

sary for  their  development,  they  multiply  rapidly.     Pasteur  has 

made  decisive  experiments  on  this  point.      He  planted  some 

yeast  cells  in  a  solution  of  sugar  to  which  he  had  added  a  small 

quantity  of  an  ammoniacal  salt  and  some  phosphates.    The  solu- 

tion of  sugar  fermented,  and  the  ferment  developed  by  budding, 

the   new    cells    absorbing   the 

ammonia  and  the  phosphates. 

They  obtained  from  the  sugar 

the   matter  necessary  to  form 

cellulose,  and  from  the  ammo- 

nia the  nitrogen  required  for 

the  elaboration  of  the  albumi- 

noid matters.     However,  these 

artificial    conditions    are    not 

those  which  are  best  adapted 

for  the  propagation  of  the  cells. 

The  latter  increase  with    ex- 

treme energy  in  liquids  which 

contain,  besides  the  yeast,  glu- 

cose, and  a  small  quantity  of  FIG.  125. 

albuminoid  matter  ready  formed. 

Lactic  Fermentation.  —  This  fermentation,  of  which  the 
conditions  have  already  been  indicated  (page  540),  is  accom- 
plished by  the  action  of  a  peculiar  ferment  of  vegetable  char- 
acter. It  is  formed  of  small  round  or  elongated  cells,  very 
short,  and  isolated,  or  in  masses.  They  are  much  smaller  than 
yeast  cells,  and  constitute  the  lactic  yeast  of  Pasteur.  It  only 
acts  upon  glucose  or  lactose  in  a  neutral  or  alkaline  liquid. 
Hence  the  necessity  of  adding  sodium  carbonate  or  chalk  to 
the  liquid.  The  reaction  consists  of  a  splitting  of  the  glucose 
molecule. 


6    =     2C3H603 

Glucose.  Lactic  acid. 

Butyric  Fermentation.  —  This  consists  in  the  transformation 
of  calcium  lactate  into  butyrate,  —  a  transformation  that  is  ac- 
companied by  a  disengagement  of  hydrogen.  According  to 
Pasteur,  this  fermentation  is  caused  by  infusoria,  and  the  ani- 
malculse  live  and  are  developed  in  situations  where  they  are 
deprived  of  free  oxygen.  Such  is  the  energy  of  their  respira- 
tory functions  that  free  oxygen  kills  them  (Pasteur).  They 
z  49 


578  ELEMENTS    OF    MODERN    CHEMISTRY. 

respire  by  decomposing  oxidized  bodies  and  assimilating  the 
oxygen. 

We  have  already  considered  the  acetic  fermentation.  We 
may  add  that  by  the  action  of  a  peculiar  ferment,  glucose  is 
converted  into  mannite  and  a  gummy  matter,  very  soluble  in 
water,  and  which  gives  a  viscous  consistence  to  the  fermented 
liquid.  This  is  called  the  viscous  fermentation. 

FERMENTED  BEVERAGES. — The  foregoing  summary  indi- 
cations regarding  fermentation  may  be  completed  by  some 
general  notions  upon  the  fermented  beverages,  particularly 
wine  and  beer. 

Wine, — It  is  universally  known  that  wine  is  the  product  of 
the  fermentation  of  grape-juice.  This  juice  contains  in  solu- 
tion inverted  sugar,  a  small  trace  of  gummy  matters,  vegetable 
albumen,  a  trace  of  fatty  matters,  coloring  matters,  free  tar- 
taric and  malic  acids,  and  various  tartrates,  principally  potas- 
sium acid-tartrate,  or  cream  of  tartar. 

The  clarified  wine  which  results  from  the  fermentation  of 
this  juice  contains,  independently  of  water,  various  products, 
some  of  which  existed  in  the  juice,  and  others  which  are  the 
results  of  the  transformation  through  which  it  has  passed. 
Among  the  first  are  the  mineral  and  vegetable  salts  of  the  juice 
(in  smaller  proportion,  because  they  are  partly  deposited  with 
the  lees),  the  gummy  matter,  a  small  quantity  of  fatty  and 
albuminoid  substances,  the  coloring  matters,  free  tartaric  and 
malic  acids,  and  the  tannin  derived  from  the  grape-stems  and 
from  the  skins  and  seeds.  Among  the  substances  which  result 
from  the  fermentation  are : 

1.  Alcohol,  which  is  the  principal  product. 

2.  Carbonic  acid  gas ;  it  is  well  known  that  it  exists  abun- 
dantly in  champagnes. 

3.  Small  quantities  of  aldehyde  and  acetic  acid  produced  by 
oxidation  of  the  alcohol.     The  acetic  acid  reacts  upon  the 
alcohol  contained  in  the  wine,  forming  acetic  ether. 

4.  Glycerin  and  succinic  acid,  in  small  quantities  (Pasteur). 

5.  Traces  of  compound  ethers,  which  contribute  to  the  bouquet 
of  the  wine.     Besides  acetic  ether,  traces  of  a  compound  ether 
called  cenanthic  ether  have  been  found  in  wine  ;  it  appears  to 
be  pelargonic  ether,  C9H1702( C2H5 ).     Berthelot  states  the  exist- 
ence of  but  slightly  volatile  acid  ethers  (malic,  tartaric)  in  wine. 

The  following  table  indicates  the  quantities  by  volume  of 
pure  alcohol  contained  in  100  volumes  of  various  wines : 


FERMENTATION.  579 

Madeira 20.48 

Port 20.22 

Roussillon 16.67 

Hermitage  (white) 16.03 

Malaga 15.87 

Saint-Georges 15.00 

Sauterne  (white) 15.00 

Cyprus 15.00 

Lunel 14.27 

Graves 12.30 

Frontignan 11.76 

Champagne 11.60 

Rhine 11.11 

Strongest  Bordeaux 11.00 

Lightest          " 7.5  to  8 

Red  Bourgogne 7.66 

Red  Macon 7.66 

Red  Chablis 7.83 

Beer. — Beer  is  a  fermented  beverage,  made  from  a  wort  of 
germinated  barley,  and  ordinarily  rendered  aromatic  by  hops. 
Like  all  other  cereals,  barley  contains  a  considerable  proportion 
of  starch.     During  the  germination,'this  starch  is  partially  con- 
verted into  maltose  by  the  action  of  a  nitrogenized  matter, 
which  is  formed  in  the  sprouting  grains,  and  which  is  called 
diastase.     In  order  to  saccharify  the  barley,  it  is  then  first 
necessary  to  cause  it  to  germinate,  and  for  this  purpose  it  is 
moistened  with  water,  and  kept  for  some  time  at 
a  temperature  of  14  or  15°  ;  the  object  of  this 
operation,  called  malting,  is  the  development  of 
the  diastase  necessary  for  the  saccharification 
of  the  starchy  matter.     When  the  sprout  has 
acquired  about  the  same  length  as  the  grain 
(Fig.  126),  the  germination  is  arrested  by  ex- 
posing the  malt  to  the  action  of  a  temperature 
of  about  50°.     The  dry  malt  is  then  reduced 
to  a  coarse  powder,  placed  in  a  large  vat,  and         Fio.  126. 
brewed  for  about  three  hours  with  water  heated 
to  50  or  60°.     In  this  operation,  the  diastase  of  the  malt  con- 
verts the  starch  into  dextrin  and  maltose,  which  dissolve,  to- 
gether with  the  other  soluble  principles  of  the  grain. 

The  sweet  wort  thus  obtained  is  heated  with  hops,  which 
yield  to  it  their  essential  aromatic  oil.  It  is  then  properly 
cooled  and  allowed  to  ferment  in  deep  vats,  into  which  a  cer- 
tain quantity  of  yeast  produced  in  a  previous  operation  is  in- 
troduced at  the  same  time.  The  alcoholic  fermentation  soon 
begins  and  goes  on  with  great  activity  during  a  few  days.  As 


580  ELEMENTS   OF   MODERN   CHEMISTRY. 

soon  as  it  has  ceased,  the  liquid  can  be  delivered  for  consump- 
tion. The  quality  of  beer  is  better  when  the  fermentation 
takes  place  at  a  low  temperature. 

Beer  contains  much  water,  free  carbonic  acid  gas,  alcohol  (2 
to  5  per  cent.),  variable  quantities  of  saccharine  matters,  dex- 
trin, nitrogenized  matters,  extractive,  bitter,  and  coloring  mat- 
ters, essential  oil,  and  various  salts. 

STARCH. 

C6H10O5 

Starch  is  universally  diffused  throughout  the  vegetable  king- 
dom. It  is  especially  abundant  in  the  seeds  of  leguminous 
plants  and  cereals,  and  in  the  potato. 

Extraction. — To  extract  starch  from  potatoes,  they  are  re- 
duced to  pulp  by  means  of  a  rasp,  and  the  pulp  is  placed  in  a 
sieve  and  washed  by  a  stream  of  water.  The  water  carries 
with  it  the  fine  granules  of  starch,  while  the  torn  cells  of  the 
potato  remain  in  the  sieve.  The  starch  gradually  deposits 
from  the  water,  and  collects  in  the  bottom  of  the  vessel,  where 
it  settles,  forming  a  cake  from  which  the  supernatent  water 
may  be  separated  by  decantation. 

Starch  may  be  extracted  from  wheat  by  making  a  paste  of 
flour  and  kneeding  it  in  a  sieve  under  a  jet  of  water :  the  starch 
granules  are  carried  with  the  water,  and  a  soft,  gray,  elastic 
mass  remains  in  the  sieve,  constituting  the  nitrogenized  matter 
of  the  flour,  or  gluten. 

Another  process,  almost  abandoned  at  present  on  account  of 
its  offensiveness,  consists  in  allowing  the  coarsely-ground  grain 
to  putrefy.  Putrefaction  destroys  the  gluten,  while  the  starch 
resists  decomposition. 

Physical  Properties. — Starch  is  a  white  powder,  formed  of 
granules  which  present  an  organic  structure.  Their  size  and 
shape  are  variable  (Fig.  127),  their  diameter  being  from  2  to  185 
thousandths  of  a  millimetre.  Those  of  potato  starch  are  larger 
than  those  of  starch  from  grain.  These  granules  are  made  up 
of  concentric  layers,  which  are  more  dense  as  they  are  nearer 
the  surface.  It  is  easy  to  make  this  structure  apparent  by 
causing  the  granules  to  undergo  a  partial  disintegration  by  the 
action  of  hot  water.  Thy  swell  up,  burst  open,  and  separate 
into  thin  layers,  as  shown  in  Fig.  128. 


STARCH.  581 

Chemical  Properties. — Starch  is  insoluble  in  water,  alcohol, 
and  ether.  Contact  with  water  heated  to  60  or  70°  causes  it 
to  swell  up  considerably,  without  dissolving.  A  semi-trans- 
parent, gelatinous  mass  results,  which  is  known  as  starch  paste. 
When  starch  is  boiled  with  a  large  quantity  of  water  and  the 
whole  is  thrown  on  a  filter,  the  liquid  which  passes  is  slightly 
turbid,  and  constitutes  what  is  known  as  solution  of  starch. 
It  contains  in  suspension  flakes  of  amylaceous  matter  small 
enough  to  pass  through  the  filter.  It  also  contains  a  small 
quantity  of  soluble  starch  (see  farther  on). 

If  a  few  drops  of  iodine  be  added  to  solution  of  starch,  a 
deep-blue  color  is  at  once  produced.  This  blue  color  disappears 
when  the  liquid  is  heated  to  90°,  and  reappears  on  cooling.  If 
a  few  drops  of  a  neutral  solution  of  calcium  chloride  be  added 
to  the  liquid,  dark-blue  flakes  are  precipitated,  constituting 
what  is  called  iodide  of  starch.  It  is  starch  dyed  by  iodine. 


FIG.  128. 

Metamorphoses  of  Starch — Dextrin. — When  long  heated 
to  100°  starch  is  converted  into  soluble  starch,  which  yields  a 
blue  color  with  iodine  (Maschke). 

Between  160  and  200°  it  is  converted  into  a  body  which  is 
very  soluble  in  water,  and  the  solution  of  which  is  not  colored 
by  iodine.  This  solution  strongly  turns  the  plane  of  polariza- 
tion to  the  right ;  hence  the  name  dextrin  given  to  this  body, 
which  is  regarded  as  isomeric  with  starch,  (C6H1005)n.  A  very 
concentrated  solution  of  dextrin  has  the  appearance  of  a  solu- 
tion of  gum.  It  is  used  as  a  mucilage  for  labels,  and  for  the 
preparation  of  immovable  surgical  dressings. 

Alcohol  added  to  a  solution  of  dextrin  precipitates  the  latter 
substance  in  the  form  of  flakes.  Subacetate  of  lead  does  not 

49* 


582  ELEMENTS   OP   MODERN   CHEMISTRY. 

precipitate  dextrin,  a  character  which  permits  the  latter  body 
to  be  distinguished  from  gum  arabic. 

When  starch  is  boiled  with  water  containing  a  few  per  cent. 
of  sulphuric  acid,  it  is  first  converted  into  dextrin,  then  into 
glucose.  It  is  generally  considered  that  the  dextrin  is  formed 
by  a  simple  molecular  transformation  of  the  elements  of  thq 
starch,  and  that  the  glucose  is  then  produced  by  the  simple 
fixation  of  one  molecule  of  water. 


5         _|_         JJ2Q        = 

Starch.  Glucose. 

According  to  Musculus,  this  is  not  the  case  ;  but  soluble 
starch  is  the  result  of  a  metameric  transformation  of  starch, 
and  subsequently  is  converted  into  dextrin  and  glucose  by  a 
true  decomposition. 


C18H30Q15        _j_         JJ2Q        = 

Starch.  Dextrin.  Glucose. 

By  the  prolonged  action  of  the  acid,  the  dextrin  itself  is 
converted  into  glucose. 

The  transformation  of  starch  into  dextrin  and  saccharine 
matter  (maltose)  takes  place  easily  under  the  influence  of  a 
peculiar  ferment  which  is  developed  in  grain  during  germina- 
tion, and  to  which  the  name  diastase  has  been  given.  It 
may  be  obtained  by  precipitating  aqueous  extract  of  malt  by 
alcohol. 

If  starch  be  triturated  with  one  and  a  half  times  its  weight 
of  concentrated  sulphuric  acid,  avoiding  an  elevation  of  tem- 
perature, and  the  mixture  be  left  to  itself  for  half  an  hour  and 
alcohol  then  added,  a  substance  is  precipitated  which  is  soluble 
in  water  and  assumes  a  rich  blue  tint  by  the  action  of  iodine. 
It  is  soluble  starch  (Bechamp). 

Starch  dissolves  abundantly  in  monohydrated  nitric  acid, 
and  water  precipitates  from  this  solution  a  white  substance, 
which,  after  washing  and  drying,  constitutes  xyloidin.  It  is 
mononitro-starch,  and  results  from  the  substitution  of  a  group 
NO2,  for  one  atom  of  hydrogen  in  starch. 


_|_HN03    =     H20     +     C6H9(N02)05 

Starch.  Xyloidin. 

Xyloidin  burns  with  deflagration  when  heated  to  180°. 


INULIN — GLYCOGEN — GUMS.  583 

INULIN. 

C«H10O5 

This  body  also  is  largely  diffused  throughout  the  vegetable 
kingdom.  It  exists  in  the  roots  of  the  elecampane  (Irnila 
kelenium),  chicory,  and  Spanish  chamomile,  in  the  bulbs  of 
colchicum,  the  tubers  of  the  dahlia,  in  the  Jerusalem  arti- 
choke, etc.  It  may  be  extracted  from  the  tubers  of  the  dahlia 
by  reducing  them  to  a  pulp  and  washing  the  latter  in  a  sieve 
under  a  stream  of  water.  The  milky  liquid  which  passes 
through  deposits  the  inulin,  which  consists  of  granules  analo- 
gous t<5  those  of  starch.  It  swells  in  cold  water,  in  which  it 
is  very  slightly  soluble.  It  is  very  soluble  in  boiling  water, 
which  again  deposits  it  in  a  pulverulent  form  on  cooling.  The 
aqueous  solution  turns  the  plane  of  polarization  to  the  left. 
It  is  not  colored  blue  by  iodine,  which  communicates  to  it  a 
fugitive,  yellow-brown  tint. 

By  long  boiling  with  water,  or  by  the  action  of  dilute  acids, 
inulin  is  converted  into  levulose. 

GLYCOGEN. 
C6H10O5 

This  body,  isomeric  with  cellulose  and  starch,  exists  in  the 
animal  economy.  Claude  Bernard  discovered  it  in  the  liver, 
and  afterwards  in  the  placenta.  It  exists  also  in  many  organs 
during  the  foetal  life.  Nearly  pure  glycogen  may  be  obtained 
by  adding  a  large  quantity  of  crystallizable  acetic  acid  to  a  cold 
and  concentrated  decoction  of  liver.  It  is  also  precipitated 
when  alcohol  is  added  to  an  aqueous  decoction  of  liver.  In  a 
pure  state,  it  is  a  white,  amorphous  powder.  When  dried  in 
the  air,  it  has  the  composition  C6H1206  (E.  Pelouze).  At  100° 
it  loses  one  molecule  of  water. 

With  water  it  forms  an  opalescent  liquid.  Alcohol  and 
ether  do  not  dissolve  it.  Boiling  with  dilute  acids  converts  it 
into  glucose.  Iodine  communicates  to  it  a  violet  or  brown-red 
color. 

GUMS. 

By  the  names  gums  and  mucilages  are  understood  certain 
substances  existing  everywhere  in  the  vegetable  kingdom,  and 
which  dissolve  or  swell  up  in  water,  giving  a  mucilaginous 


584  ELEMENTS   OF   MODERN   CHEMISTRY. 

consistence  to  the  liquid.  The  gums  proper  are  distinguished 
from  the  mucilaginous  substances,  which  are  not  really  soluble. 
Both  furnish  mucic  and  oxalic  acids  when  treated  with  nitric 
acid.  Gum  furnishes  at  the  same  time  a  small  quantity  of 
tartaric  acid. 

Gum  Arabic. — Gum  arabic  is  identical  with  Senegal  gum. 
It  flows  naturally  from  different  species  of  acacia.  It  dissolves 
abundantly  in  cold  water  and  is  precipitated  from  its  solution 
by  alcohol.  Fremy  considers  that  it  is  composed  essentially  of 
the  calcium  and  potassium  salts  of  an  acid  which  he  designates 
as  gummic  add  (arabiri). 

When  dried  at  100°,  the  latter  body  has  the  composition 
indicated  by  the  formula  C12H220U.  It  is  very  soluble  in 
water,  and  its  solution  rotates  the  plane  of  polarization  to  the 
left. 

When  heated  to  120-150°,  it  becomes  insoluble  in  water 
and  is  converted  into  metagummic  add.  According  to  Fremy, 
the  gum  of  cherry-  and  plum-trees  is  a  mixture  of  gummates, 
which  are  soluble  in  cold  water,  and  insoluble  metagummates. 
The  metagummates  are  insoluble  in  water,  but  when  boiled 
with  that  liquid  are  transformed  into  soluble  gummates. 

Subacetate  of  lead  forms  an  abundant  white  precipitate  in 
solutions  of  gum  arabic. 

When  gum  arabic  is  boiled  with  dilute  sulphuric  acid,  it  is 
converted  into  a  mixture  of  two  saccharine  substances ;  one  is 
uncrystallizable,  the  other  crystallizes  in  large,  colorless  rhombic 
prisms,  having  a  sweet  taste,  and  fusible  at  160°.  It  is  called 
arabinose.  It  reduces .  the  cupro-potassic  solution  and  is  not 
fermentable.  It  is  isomeric  with  glucose. 

Gum  Tragacanth. — This  gum  flows  from  the  Astragalus  of 
the  Levant  and  of  Persia.  Bassora  gum  is  derived  from  a  spe- 
cies of  cactus.  Both  contain  a  mucilaginous  matter  insoluble  in 
water,  but  which  swells  up  in  that  liquid,  forming  a  transparent 
jelly.  This  matter  is  bassorin.  With  nitric  acid,  it  yields  much 
mucic  acid.  When  boiled  with  dilute  sulphuric  acid,  it  is  readily 
converted  into  crystallizable  glucose. 

CELLULOSE. 

C6H1005 

This  name  is  given  to  the  matter  which  forms  the  walls  of 
young  vegetable  cells,  and  which  is  deposited,  mixed  with  other 


CELLULOSE.  585 

matters,  in  the  older  cells,  particularly  in  ligneous  fibre.  The 
pith  of  the  elder  and  of  ^Eschynomene  paludosa,  cotton,  old 
linen,  and  paper  are  almost  pure  cellulose. 

In  ligneous  fibres,  in  wood,  the  cellulose  is  permeated  by 
various  foreign  substances,  among  which  Payen  has  distin- 
guished the  incrusting  matter  which  thickens  the  tissues  and 
gives  them  rigidity.  Among  the  others  are  nitrogenous  mat- 
ters, resins,  various  coloring  matters,  etc.  With  these  organic 
substances  in  the  ligneous  fibres,  are  united  the  mineral  ele- 
ments which  are  found  more  or  less  modified  in  the  ashes. 

Old  linen  and  cotton  serve  for  the  preparation  of  pure 
cellulose.  Such  materials  are  boiled  with  a  weak  solution  of 
potassium  hydrate,  washed,  and  successively  exhausted  with  a 
solution  of  chlorine,  acetic  acid,  alcohol,  ether,  and  water,  and 
dried  at  100°.  The  insoluble  product  which  remains  after  this 
treatment  is  considered  as  pure  cellulose. 

Properties. — Cellulose  is  a  diaphanous,  white  solid,  of  a 
density  of  1.25  to  1.45.  It  is  insoluble  in  water,  alcohol, 
ether,  and  the  dilute  acids  and  alkalies.  It  dissolves  in  the 
cupro-ammoniacal  liquid  which  is  obtained  by  dissolving  cupric 
hydrate  or  carbonate  in  a  small  quantity  of  concentrated  am- 
monia, or  better,  by  dissolving  metallic  copper  in  ammonia  in 
contact  with  the  air  (Schweizer). 

When  submitted  to  dry  distillation,  cellulose  leaves  a  residue 
of  carbon  and  yields  numerous  gaseous  and  liquid  products. 
The  gas  obtained  by  the  distillation  of  wood  is  used  for  illu- 
minating purposes  in  some  localities.  The  liquid  product 
ordinarily  separates  into  two  layers,  one  of  which  is  aqueous 
and  contains  acetic  acid,  wood-spirit,  acetone,  etc. ;  the  other  is 
insoluble  in  water  and  constitutes  wood-tar. 

When  cellulose,  charpie  for  example,  is  sprinkled  with  con- 
centrated sulphuric  acid  and  the  mass  is  rapidly  triturated,  a 
viscous  mass,  having  but  little  color,  is  obtained ;  it  contains, 
independently  of  a  compound  of  sulphuric  acid  and  cellulose 
(sulpho-ligneous  acid),  substances  which  result  from  the  dis- 
integration of  the  cellulose.  Accordingly,  as  the  action  of  the 
acid  is  more  or  less  prolonged,  a  substance  is  obtained  which  is 
insoluble  in  water  and  colored  blue  by  iodine  and  consequently 
analogous  to  starch,  or  a  soluble  matter  analogous  to  dextrin 
(Bechamp).  When  water  is  added  to  this  viscous  mass  and 
the  whole  is  submitted  to  a  prolonged  ebullition,  fermentable 
glucose  is  formed  (Braconnot). 
z* 


586  ELEMENTS   OF   MODERN   CHEMISTRY. 


C6Hio05      +       jpo      =      C6H1206 
Cellulose.  Glucose. 

When  paper  is  dipped  into  a  cold  mixture  of  sulphuric  acid 
with  half  its  volume  of  water,  and  is  then  carefully  washed  and 
dried,  a  semi-transparent  matter  is  obtained  which  has  a  certain 
rigidity,  and  is  similar  to  parchment  in  aspect  (Figuier  and 
Poumarede,  Hofmann).  It  is  called  vegetable  parchment. 

A  cold  solution  of  chloride  of  zinc  converts  cellulose  into  an 
amyloid  matter  which  is  colored  blue  by  iodine  ;  if  heat  be 
applied,  the  whole  is  dissolved  and  glucose  is  formed. 

When  charpie  is  heated  with  a  concentrated  solution  of  cal- 
cium hypochlorite  (chloride  of  lime),  a  very  violent  reaction 
takes  place,  and  torrents  of  carbon  dioxide  are  evolved. 

Gun-  Cotton.  —  When  carded  cotton  is  immersed  for  half  a 
minute  in  monohydrated  nitric  acid,  and  then  rapidly  washed 
in  a  large  quantity  of  water  and  allowed  to  dry  in  the  air,  a 
substance  is  obtained  which  possesses  all  the  exterior  appear- 
ances of  cotton,  but  is  very  inflammable  and  burns  suddenly 
without  residue.  It  is  gun-cotton,  or  pyroxylin,  which  was 
discovered  by  Schonbein  in  1847. 

In  its  preparation,  the  monohydrated  nitric  acid  may  be 

advantageously  replaced  by  a  mixture  of  one  volume  of  fuming 

nitric  acid  and  three  volumes  of  sulphuric  acid.     Pyroxylin 

seems  to  be  a  mixture  of  dinitrocellulose  and  trinitrocellulose. 

C6Hu>O5  C6H8(N02)205  C6H7(N02)305 

Cellulose.  Dinitrocellulose.  Tri  nitrocellulose. 

Gun-cotton  looks  like  cotton,  but  is  more  harsh  to  the  touch 
and  sometimes  has  a  light  yellowish  tint.  It  burns  with  a 
sudden  flash,  leaving  no  residue,  and  produces  a  great  volume 
of  gaseous  products  consisting  of  carbon  monoxide,  carbon 
dioxide,  nitrogen  dioxide,  etc.,  and  vapor  of  water.  Gun-cotton 
is  insoluble  in  water,  alcohol,  ether,  chloroform,  and  the  cupro- 
ammoniacal  solution.  It  is  more  or  less  soluble  in  a  mixture  of 
alcohol  and  ether,  and  the  solution  is  employed  in  surgery  and 
photography  under  the  name  collodion.  Pure  trinitrocellulose 
is,  however,  insoluble  in  alcoholic  ether.  When  pyroxylin  is 
heated  with  a  concentrated  solution  of  ferrous  chloride,  nitrogen 
dioxide  is  disengaged,  and  cellulose  is  regenerated  (Bechamp). 

GLUCOSIDES. 

The  glucosides  are  complex  compounds,  which  break  up 
under  various  conditions,  fixing  the  elements  of  water  and 


GLUCOSIDES.  587 

yielding  glucose  and  other  bodies,  just  as  the  compound  ethers, 
in  fixing  the  elements  of  water,  are  decomposed  into  alcohols 
and  acids. 

This  definition  seems  to  relate  the  glucosides  to  the  com- 
pound ethers,  a  relation  with  seems  legitimate,  since  it  has 
been  shown  by  the  experiments  of  Berthelot  that  glucose  has 
the  function  of  a  polyatomic  alcohol. 

Various  immediate  principles  of  vegetable  origin  can  be 
classed  as  glucosides.  We  may  mention  particularly  the  fol- 
lowing : 

GLUCOSID-S.  FORMULAS.  ORIGIN. 

Amygdalin  ....  C20H27N011  bitter  almonds. 

Salicin      .....  C13H1807  willow  and  poplar  bark. 

Populin    .....  C2°U2208  bark  and  leaves  of  the  aspen. 

Phloridzin    ....  C21H24010  bark  and  roots  of  fruit-trees. 

Arbutin    .....  C12H1607  leaves  of  the  Arctoataphylos  uva  nrsi. 

Convolvulin  .     .     .     .  0»H<»OW  (  ..  t 

Jalappin  .....  C^R^O™  }  JaIaP-root- 

Esculm    .....  C21H2*013  bark  of  India  chestnut. 

Fraxiu      .....  C27H30017  bark  of  the  ash. 

Daphnin  .....  C31H34019  Daphne  a/pitta,  Daphne  mezerenm. 

Quinovin  .....  C^H^O8  bark  of  Ciiiim  now. 

Tannin     .....  C27H220"  oak-bark,  nut-galls,  etc. 

Among  all  of  these  bodies,  we  will  only  consider  amygdalin, 
salicin,  populin,  phloridzin,  and  tannin,  or  t-annic  acid. 

Amygdalin,  C^H^NO".—  This  body  is  extracted  from  the 
cake  of  bitter  almonds,  and  it  deposits  from  its  alcoholic  solu- 
tion in  crystals  containing  two  molecules  of  water.  Its  aqueous 
solution  allows  it  to  crystallize  in  quite  large  crystals  contain- 
ing three  molecules  of  water. 

Amygdalin  is  very  soluble  in  water  and  in  boiling  alcohol. 
Its  aqueous  solution  rotates  the  plane  of  polarization  to  the 
left. 

By  the  action  of  dilute  acids  amygdalin  is  decomposed  into 
hydrocyanic  acid,  benzoyl  hydride,  or  benzoic  aldehyde  (oil  of 
bitter  almonds),  and  glucose. 


O11  -f  2H20  =  C7H60  +    CHN    +  2C6H1206 

Amygdalin.  Benzoic  Hydrocyanic  Glucose. 

aldehyde.  acid. 

The  same  decomposition  takes  place  by  the  action  of  water 
and  a  peculiar  ferment  which  is  contained  in  both  bitter  and 
sweet  almonds,  and  which  is  called  emulsin,  or  synaptase.  It 
is  a  nitrogenized  matter,  soluble  in  water,  and  only  acts  on 
amygdalin  in  presence  of  water.  It  is  well  known,  indeed,  that 


588  ELEMENTS   OP   MODERN   CHEMISTRY. 

bitter  almonds  only  develop  the  odor  of  prussic  acid  when 
moistened  with  water. 

Salicin,  CI3H18O7.  —  Salicin  exists  already  formed  in  the  bark 
of  the  willow  and  poplar.  Wbhler  discovered  its  existence  in 
castoreum.  It  may  be  prepared  by  exhausting  willow-bark 
with  boiling  water,  concentrating  the  liquid  and  digesting  it 
with  litharge.  The  solution  is  then  filtered  and  evaporated  to 
a  syrupy  consistence  ;  the  salicin  deposits  in  a  few  days. 

It  occurs  in  small  scales,  or  brilliant  needles,  soluble  in  water 
and  alcohol  and  insoluble  in  ether.  Its  aqueous  solution  turns 
the  plane  of  polarization  to  the  left. 

Salicin  dissolves  in  sulphuric  acid,  forming  a  red  liquid. 

By  the  action  of  a  solution  of  emulsin  (the  nitrogenous  mat- 
ter of  almonds),  it  breaks  up  into  a  neutral  body  called  salige- 
nin,  and  glucose. 

Ci3Hi807  _|_  H20  =  C7H802  +  C6H1206 

Salicin.  Saligeuin.  Glucose. 

Dilute  sulphuric  and  hydrochloric  acids  decompose  it  by 
the  aid  of  heat  into  saliretin  and  glucose.  These  bodies  will 
be  described  farther  on. 

When  salicin  is  fused  with  potassium  hydrate,  hydrogen  is 
disengaged,  and  salicylic  and  oxalic  acids  are  formed. 

By  the  action  of  a  mixture  of  potassium  dichromate  and 
sulphuric  acid,  salicin  yields  carbon  dioxide,  formic  acid,  and 
an  oxidized  oil,  which  is  the  hydride  of  salicyl  or  salicylic  alde- 
hyde, C7H602  (Piria). 

Popnlin,  C20H2208  -f-  2H20.  —  Braconnot  discovered  this  sub- 
stance in  the  bark  and  leaves  of  the  aspen  (Populus  tremula). 
To  extract  it,  those  substances  are  exhausted  with  boiling  water, 
the  decoction  is  precipitated  by  subacetate  of  lead,  filtered,  and 
the  filtrate  evaporated  to  a  syrupy  consistence.  On  cooling, 
the  populin  is  deposited  as  a  crystalline  precipitate.  When 
properly  purified,  it  occurs  in  very  fine,  silky,  colorless  needles. 
Its  taste  is  sweet  ;  it  is  but  slightly  soluble  in  water,  more 
soluble  in  alcohol.  By  the  action  of  dilute  acids,  it  is  decom- 
posed into  benzoic  acid,  saliretin,  and  glucose  ;  the  latter  two 
products  result  from  the  decomposition  of  salicin,  so  that  popu- 
lin appears  to  be  a  combination  of  benzoic  acid  and  salicin. 


Populin.  Benzoic  acid.  Salicin. 

Phloridzin,  C21H24O10  -f  2H20.—  This  substance  exists  in 


GLUCOSIDES.  589 

the  bark  of  apple,  pear,  plum,  and  cherry  trees,  and  principally 
in  the  roots  of  fruit-trees.  It  may  be  extracted  by  boiling  the 
roots  with  water,  decanting  the  boiling  solution,  concentrating 
it,  and  allowing  it  to  stand  in  a  cool  place.  The  phloridzin 
deposits  on  cooling,  and  may  be  purified  by  recrystallization 
after  decolorizing  it  with  animal  charcoal. 

When  pure,  it  forms  colorless,  silky  needles,  having  a  bitter 
taste,  and  an  after-taste  which  is  sweet.  It  is  scarcely  soluble 
in  cold  water,  but  dissolves  abundantly  in  boiling  water  and 
in  alcohol.  The  alcoholic  solution  turns  the  plane  of  polariza- 
tion to  the  left. 

Dilute  sulphuric  and  hydrochloric  acids  decompose  it  into 
phloretin  and  glucose. 


(121JJ24Q10        _|_        JJ2Q        _        CJ15JJUQ5        + 
Phloridzin.  Phloretin.  Glucose. 

Phloretin  is  a  white  substance  which  crystallizes  in  little 
scales,  slightly  soluble  in  water  and  very  soluble  in  alcohol. 
When  phloretin  is  heated  with  potassium  hydrate,  it  breaks  up 
into  phloretic  acid  and  phlorogludn. 


=     C9H1003    +     C6H603 

Phloretin.  Phloretic  acid.  Phloroglucin. 

Phloroglucin  forms  large  crystals  having  a  sweet  taste. 

Tannin,  or  Tannic  Acid,  C27H2201T.  —  The  names  tannins 
and  tannic  acids  are  applied  to  certain  slightly  acid  compounds 
which  are  largely  diffused  in  the  vegetable  kingdom,  and  which 
have  two  important  properties  :  they  precipitate  solutions  of 
gelatin  and  albuminous  matters,  and  produce  a  bluish  or 
greenish-black  color  with  the  ferric  salts.  The  most  important 
of  these  compounds,  the  tannin  of  oak  bark,  or  quercitannic 
acid,  is  a  glucoside.  By  the  action  of  dilute  acids  it  is  decom- 
posed into  gallic  acid  and  glucose  (Strecker). 

Tannin  exists  in  oak  bark,  in  sumac,  and  in  large  quantities 
in  nut-galls,  which  are  excrescences  developed  by  the  sting  of 
an  insect  on  the  leaves  and  branches  of  the  Quercus  infectoria. 

It  is  prepared  by  introducing  coarsely-powdered  nut-galls  into 
a  percolator,  and  exhausting  them  with  ordinary  commercial 
ether.  The  ethereal  solution  which  passes  through  is  collected 
in  a  flask,  and  in  the  course  of  a  day  separates  into  two  or 
sometimes  three  layers.  The  lower  layer  is  a  very  concen- 
trated, aqueous  solution  of  tannin.  It  is  separated  and  dried 

50 


590  ELEMENTS   OP   MODERN    CHEMISTRY. 

in  a  hot-air  oven.     The  tannin  remains  as  a  light,  bulky  mass, 
having  a  yellowish  color. 

Tannin  is  a  colorless,  amorphous  solid,  having  a  very  astrin- 
gent taste.  It  is  very  soluble  in  water,  less  soluble  in  alcohol, 
insoluble  in  pure  ether. 

It  melts  when  heated,  and  between  210  and  215°  it  dis- 
engages carbon  dioxide  and  yields  pyrogallol,  C6H603,  which 
volatilizes.  A  black  residue  remains  (metagallic  acid). 

On  contact  with  the  air,  the  aqueous  solution  of  tannic  acid 
absorbs  oxygen,  disengages  carbon  dioxide,  and  deposits  gallic 
acid.     This  transformation  takes  place  more  rapidly  when  oak 
tannin  is  boiled  with  dilute  sulphuric  or  hydrochloric  acid. 
C27H220i7     +     4H20     =     3C7H605     +     C6H1206 

Tannin.  Gallic  acid.  Glucose. 

The  researches  of  H.  Schiff  seem  to  show  that  tannin,  prop- 
erly speaking,  is  not  a  glucoside  but  is  digattic  acid,  CUH100', 
that  is,  an  acid  derived  from  two  molecules  of  gallic  acid  by  the 
subtraction  of  one  molecule  of  water.  By  fixing  the  elements 
of  water,  a  molecule  of  tannin  would  form  two  molecules  of 
gallic  acid. 

C14H10()9        _|_         H2Q        =        2C7H605 
Digallic  acid.  Gallic  acid. 

A  solution  of  tannic  acid  produces  with  ferric  salts  a  bluish- 
black  precipitate,  which  constitutes  ink.  Tannin  does  not  color 
ferrous  salts,  but  the  mixture  soon  blackens  on  exposure  to  the 
air  by  absorbing  oxygen. 

Tannin  is  employed  in  medicine  as  an  astringent.  Nut-galls, 
which  are  very  rich  in  tannin,  are  used  for  the  manufacture  of 
ink.  A  good  ink  may  be  prepared  by  the  following  receipt: 
One  kilogramme  of  powdered  nut-galls  is  exhausted  with  14  litres 
of  water ;  the  solution  is  filtered,  and  a  solution  of  500  grammes 
of  gum  arabic  is  first  added,  then  a  solution  of  500  grammes  of 
ferrous  sulphate  (green  vitriol).  The  mixture  is  well  stirred  up, 
and  then  exposed  to  the  air  until  it  has  acquired  a  fine  black  color. 


AROMATIC   COMPOUNDS. 

The  compounds  which  we  have  studied  thus  far  are  rich  in 
atoms  of  hydrogen.  Most  of  them  are  saturated  or  derived 
from  saturated  compounds.  The  hydrocarbons  of  the  series 
CnH2n+2,  the  alcohols  CnH2n+20,  the  fatty  acids  CnH2n02,  are 


AROMATIC   COMPOUNDS.  591 

of  these  classes  of  compounds  the  most  rich  in  hydrogen  that 
are  known  ;  they  belong  to  what  is  called  the  fatty  series.  But 
there  are  other  compounds  which  possess,  like  the  preceding, 
the  characters  of  hydrocarbons,  alcohols,  and  acids,  in  which 
the  relation  between  the  atoms  of  carbon  and  of  hydrogen  is  not 
the  same.  The  atoms  of  the  latter  element  decrease  in  num- 
ber in  proportion  to  those  of  the  former.  These  relations  may 
be  understood  by  a  glance  at  the  following  formulae  : 

C10R22  decane.  C10HM0  decyl  hydrate. 

C10H20  decylene.  C10HM0  mint  camphor. 

C10H!8  menthene.  C10H180  Borneo  camphor. 

C10Hie  turpentine.  C^flWO  ordinary  camphor. 

C10H"  cymene.  C10H"0  thymol. 

C10H8    naphthalene.  C10H120  cuminic  aldehyde. 

A  large  number  of  these  unsaturated  compounds  belong 
or  are  related  to  those  aromatic  substances  which  are  called 
essences  or  essential  oils.  Hence  the  name  aromatic  com- 
pounds, which  has  been  given  to  all  of  these  bodies  containing 
but  little  hydrogen. 

The  most  interesting  of  the  hydrocarbons  of  the  aromatic 
series  is  benzol,  which  is  now  obtained  in  large  quantities  from 
coal-tar.  It  is  as  important  by  reason  of  the  applications  which 
it  has  received  in  the  arts  as  on  account  of  the  theoretical  con- 
siderations which  attach  to  it.  Kekule  has  made  it  the  centre 
of  the  aromatic  series  which  would  include,  in  a  limited  sense, 
only  the  derivatives  of  benzol.  In  a  word,  the  latter  body  is 
the  nucleus  of  all  the  aromatic  compounds. 

Kekule's  theory  considers  that  the  6  atoms  of  carbon  of 
benzol  form  a  closed  chain,  each  being  bound  to  its  neighbors, 
on  one  side  by  one,  and  on  the  other  by  two  bonds  of  saturation. 
One  atom  of  hydrogen  is  attached  to  each  of  these  carbon  atoms. 

H 

A 

H-C      C-H 

H-C      C-H 

V 


Benzol.* 

*  In  this  formula,  the  connecting  lines  indicate  the  saturation  of  the 
atomicities  ;  the  double  lines  indicate  the  exchange  of  two  atomicities 
between  two  neighboring  atoms  of  carbon. 


592  ELEMENTS   OF    MODERN    CHEMISTRY. 

Very  numerous  and  very  different  aromatic  compounds  are 
derived  by  the  substitution  of  different  elements  or  groups  for 
the  hydrogen  atoms  in  the  molecule  of  benzol,  that  molecule 
forming,  so  to  speak,  the  nucleus  of  all  the  aromatic  com- 
pounds. 

1.  If  one  atom  of  hydrogen  be  replaced  by  chlorine  or  bro- 
mine, monochlorobenzol  or  monobromobenzol  will  result,  these 
compounds  being  also  called  chloride  and  bromide  of  phenyl. 

C6He  C6H5C1  C6H5Br 

Benzol.  Monochlorobenzol.          Mohobroinobenzol. 

2.  If  one  atom  of  hydrogen  be  replaced  by  the  group  hy- 
droxyl  (OH),  phenol,  or  phenyl  hydrate,  is  formed.     The  sub- 
stitution of  two  hydroxyl  groups  for  two  atoms  of  hydrogen 
produces  the  oxyphenols  ;  that  of  three  groups  OH  for  three 
atoms  of  hydrogen  produces  phloroglucin  (page  618). 

/OH 

oJJ  C6IP<-OH 

OH 

Benzol.  Phenol.  Oxyphenol  and  Phloroglucin  and 

its  isomerides.  its  isomerides. 

3.  The  substitution  of  one  or  more  groups  (NO2)'  for  one 
or  more  atoms  of  hydrogen  gives  rise  to  the  nitro-derivatives. 


Benzol.  Nitrobenzol.  Dinitrobenzol. 

4.  The  substitution  of  the  group  (NH2)  for  one  atom  of 
hydrogen  produces  phenylamine,  or  aniline  ;  that  of  two  groups 
NH2  for  two  atoms  of  hydrogen  yields  phenylene-diamine. 

C6H6  C6H5-NH2 


Benzol.  Phenylamine  (aniline).        Phenylene-diamine 

and  its  isomerides. 

5.  If  one  or  more  atoms  of  hydrogen  in  benzol  be  replaced 
by  as  many  methyl  groups,  CH3,  the  superior  homologues  of 
benzol  are  obtained. 

C«H«    =    C6H6  benzol. 

C7H8    =    C6H5-CH3      toluol  (methylbenzol). 

PH3 

C8H10  =    C«H4<3  xylol  and  isomerides  (dimethylbenzols). 


C9HU  =    C6H3—  CH3  mesitylene  and  isomerides  (trimethylbenzols). 

^CH3 
C12H18=    C(CH3)6         hexamethylbenzol. 

One  ethyl  group  can  replace  one  atom  of  hydrogen  in  ben- 


AROMATIC   COMPOUNDS.  593 

zol,  and  ethylbenzol,  which  is  isomeric  with  dimethylbenzol, 
would  result. 


Ethylbenzol.  Dimethylbenzol. 

There  are  many  instances  of  such  isomerisin,  and  they  re- 
ceive the  same  interpretation. 

One  atom  of  hydrogen  in  benzol  may  be  replaced  by  a  propyl 
group,  C3H7,  and  propyl  benzol,  which  is  isomeric  with  trimethyl- 
benzol,  is  the  result. 

One  atom  of  hydrogen  may  be  replaced  by  an  ethyl  group 
and  another  by  a  methyl  group,  and  the  new  compound  would 
be  ethyl-methylbenzol,  isomeric  with  propylbenzol  and  with  tri- 
rnethylbenzol. 

^ITS  /-CH3 

C6H5-C3HT  C«H*<™  C«H3—  CH3 

^-CII8 

Propylbenzol  (cunienf).  Ethyl-methylbenzol.  Trimethylbenzol. 

These  alcoholic  radicals  which  are  thus  substituted  for  the 
hydrogen  of  benzol,  constitute,  according  to  the  expression  of 
Kekule,  lateral  chains,  which  are  grafted,  so  to  speak,  on  the 
benzol  nucleus  or  principal  chain. 

6.  The  aromatic  acids,  properly  speaking,  result  from  the 
substitution  of  one  or  more  carboxyl  groups,  CO.OH  =  C02H, 
for  one  or  more  hydrogen  atoms  in  the  benzol  nucleus. 

C«H<>        C«H5-C02H        C6H*<  C6H3(C02H)3       C«(C02H)6 


Benzol.       Ben/oic  acid.  Phthalic  acid  Trimesic  acid         Mellic  acid. 

and  isomerides.          and  isomerides. 

7.  In  the  homologues  of  benzol,  the  substitution  of  Cl,  Br, 
OH,  NH2,  C02H,  etc.,  for  hydrogen,  may  take  place  either  in 
the  benzol  nucleus  or  in  the  lateral  chain  :  isomeric  compounds 
are  thus  formed. 

a.  By  substitution  of  one  atom  of  chlorine  for  an  atom  of 
hydrogen  in  toluol,  two  isomeric  compounds,  C7H7C1,  may  be 
obtained.     In  one,  the  chlorine  will  be  attached  to  the  lateral 
chain  ;  in  the  other,  it  will  be  attached  to  the  benzol  nucleus, 
as  is  the  group  CH3  itself. 

C«H»-CH»  OT'-CIPCI  C«H*<^H3 

Toluol.  Benzyl  chloride.  Chlorotoliiol. 

b.  The  phenols  result  from  the  substitution  of  OH  for  an 
atom  of  hydrogen  in  the  nucleus.     If  this  substitution  take 
place  in  a  lateral  chain,  an  aromatic  alcohol,  isomeric  with  the 
corresponding  phenol,  is  obtained. 

50* 


594  ELEMENTS   OF   MODERN    CHEMISTRY. 


Toluul.  Benzylic  alcohol.  Crcsol. 

c.  The  substitution  of  a  carboxyl  group,  C02H,  for  an  atom 
of  hydrogen  in  the  benzol  nucleus  of  toluol,  C6H5-CH3,  pro- 
duces the  aromatic  acids,  toluic  acid,  and  its  isomerides  ;  if, 
however,  the  carboxyl  replace  a  hydrogen  atom  in  the  lateral 
chain,  CH3,  alpha-toluic  acid,  isonieric  with  the  preceding  acids, 
results. 


Toluol.  Toluic  acids.  a-toluic  acid. 

d.  When  two  groups  OH  are  substituted  for  two  atoms  of 
hydrogen  in  the  principal  chain,  oxyphenols  are  formed. 

/CH3 
C«H3-OH 
^OU 
Orcin. 

e.  The  substitution  of  the  group  NH2  for  one  atom  of  hydro- 
gen in  the  principal  chain,  on  the  one  hand,  and  in  the  lateral 
chain,  on  the  other,  produces  isomeric  alkaloids. 


C6H5-CH(NH2) 

Benzylamine.  Toluidine. 

8.  This  is  not  all  ;  the  lateral  chains  may  be  grafted  at  dif- 
ferent points  of  the  benzol  nucleus  by  substitution  for  the  dif- 
ferent hydrogen  atoms.  Their  positions  and  their  relative  dis- 
tances from  each  other  are  the  causes  of  numerous  isomerisms. 

It  is  important  to  understand  the  principle  of  this  isomer- 
ism.  Let  us  consider  the  most  simple  case,  that  in  which 
two  atoms  of  hydrogen  are  replaced  by  two  other  mon  atomic 
atoms  or  monatomic  groups.  Such  compounds  are  the  di- 
substituted  derivatives  of  benzol,  and  experiment  has  shown 
that  there  are  three  di-substituted  derivatives  of  each  kind. 

Thus  there  are  three  hydrocarbons  containing  two  groups 
CH3,  each  substituted  for  one  atom  of  hydrogen  in  benzol  ; 
three  phenols,  each  containing  two  groups  OH  ;  three  acids, 
each  containing  one  group  CO2H,  and  one  group  OH,  substi- 
tuted each  for  one  atom  of  hydrogen,  and  three  acids,  each 
containing  two  carboxyl  groups  substituted  for  two  atoms  of 
hydrogen.  Indeed,  this  substitution  may  take  place  in  three 
different  ways.  The  six  carbon  atoms  forming  a  closed  chain 
and  a  hydrogen  atom  being  attached  to  each  carbon,  the  re- 


AROMATIC   COMPOUNDS. 


595 


placement  of  two  atoms  of  hydrogen  may  affect  two  adjoin- 
ing atoms  of  carbon,  or  two  atoms  of  carbon  separated  by  a 
third  atom  of  carbon  which  still  retains  its  H,  or  lastly,  two 
carbon  atoms  which  are  separated  by  two  other  carbon  atoms, 
each  of  which  still  retains  its  H.  The  relative  positions  of  the 
groups  being  different  in  each  case,  it  results  that  the  molecules 
present  different  structures  and  are  consequently  isomeric.  The 
following  examples  will  explain  this  kind  of  isomerism. 

OrtAo-derivatives  are  those  in  which  the  hydrogen  of  two 
adjacent  carbon  atoms  is  replaced;  raeta-derivatives  are  those 
in  which  the  two  carbon  atoms  affected  are  separated  by  a  third ; 
para-derivatives  are  those  in  which  the  two  carbon  atoms  are 
separated  by  two  others. 


02 

CH3 

OH 

OH 

C02H 

W 
> 

A 

A 

A 

A 

|j 

HC      C-CH3 

HC      C-OH 

HC      C-C02H 

HC    c-com 

s 

HC^    OH 

HCx  J3H 

HCK    CH 

HC      CH 

B 

^  / 

^      / 

Q 

V 

c 

C 

C 

6 

H 

H 

H 

H 

H 

Orthoxylol. 

Orthodiphenol 

Orthoxybenzoic 

Orthophthalic 

P5 

(pyrocatechin). 

acid 

acid 

O 

(salicylic). 

(phthalic). 

CH3 

OH 

OH 

C02H 

™ 

i 
^C 

A 

C 

c 

//  \ 

/,  \ 

H 

HC'  NCH 

KG   SCH 

HC      CH 

HC      CH 

£ 

HCx    C-CH3 

HCs    C-OH 

HC      C-C02H 

HC      C-C02H 

V      / 

^     / 

^ 

xxcx 

*c' 

C 

C 

^ 

H 

H 

H 

H 

1 

Metaxylol. 

Metadiphenol 
(resorcin). 

Metoxybenzoic 
acid 

Metaphthalic  acid 
(isophthalic). 

(oxybenzoic). 

S 

CH3 

OH 

OH 

C02H 

£ 

A 

A 

C 

//Cx 

H 

//  \ 

IICX    CH 

HC'    CH 

HC      CH 

HCX  SCH 

3 

H6      CH 

HC      CH 

HCxN    CH 

HCs    CH. 

— 

A,      / 

•^  / 

« 

C 

C 

^G 

*C 

3 

CH3 

OH 

C02H 

C02H 

P] 

Paraxylol. 

Paradiphenol 

Paroxybenzoic 

Pai-aphthalic  acid 

(hydroquinone). 

acid. 

(teraphthalic). 

596  ELEMENTS    OP    MODERN    CHEMISTRY*. 

These  indications  will  suffice  to  illustrate  the  class  of  isomer- 
ides  under  consideration.  With  the  tri -substituted  derivatives 
of  benzol,  theory  foresees  and  experiment  has  demonstrated  the 
existence  of  still  more  numerous  isomerides,  but  we  cannot 
dwell  on  them  here. 

Two  very  important  hydrocarbons  are  now  considered  as 
directly  related  to  benzol.  They  are  naphthalene,  C10H8,  and 
anthracene,  CUH10. 

Naphthalene  is  formed  by  the  union  of  two  benzol  nuclei, 
two  atoms  of  carbon  being  common  to  each  nucleus  (Erlen- 
ineyer). 

Anthracene  results  from  the  union  of  two  benzol  nuclei  by 
the  intermediation  of  two  carbon  atoms,  which  are  themselves 
combined  together,  each  by  one  atomicity,  and  each  of  which 
is  combined  with  one  atom  of  hydrogen  (Graebe). 

These  ideas  are  indicated  in  the  following  graphic  formulae, 
which  express  the  reciprocal  relations  between  the  atoms  of 
carbon  and  hydrogen,  but  not  their  real  positions  in  space.  The 
latter  might  be  better  indicated  by  a  polyhedral  form. 

H          H  H          H     H 
,C  C   C  C   H   C 

'/  ^  //  \  /  *\  //  \    i   /  >N 

HC   CH      HC   C   CH       HC  C-C-C  CH 
HC   CH      HC   C   CH       HC  C-C-C  CH 

v  v  v          y  H  v 

H  H 

Benzol.  Naphthalene.  Anthracene. 

We  must  with  these  brief  indications  conclude  the  considera- 
tion of  the  principles  of  Kekule's  theory,  which  includes  very 
many  compounds.  These  are  the  aromatic  compounds  in  the 
strict,  sense  of  the  word.  Before  undertaking  their  study,  we 
will  briefly  describe  oil  of  turpentine  and  some  of  the  bodies 
allied  to  it. 

OIL  OF   TURPENTINE  AND  ITS  ISOMERIDES. 

A  large  number  of  hydrocarbons  are  known  having  the  com- 
position C10H16.  Some  are  the  natural  products  which  consti- 
tute the  whole  or  part  of  the  numerous  essential  oils.  Others 
are  the  products  of  art. 

Among  the  first  are  the  oils  of  turpentine,  lemon,  orange, 
bergamot,  orange-flower,  juniper,  savin,  lavender,  cubebs,  co- 
paiba, eleini,  pepper,  cloves,  etc. 


TURPENTINE. 


59V 


These  oils  are  liquids ;  some  of  them  are  mixed  with  oxy- 
genized solid  bodies  which  are  deposited  in  time,  and  which 
were  formerly  designated  as  stearoptenes. 

They  are  obtained  by  distilling  the  vegetable  products  which 
contain  them  with  water,  for,  although  the  boiling-points  of 
these  oils  are  between  150  and  200°,  they  distil  readily  with 
aqueous  vapor,  and  collect  in  the  form  of  a  layer  on  the  sur- 
face of  the  condensed  water. 

The  more  ordinary  process  consists  in  passing  a  current  of 
steam  through  the  plants  or  aromatic  vegetables.  For  this 
purpose  they  are  placed  on  a  diaphragm,  M  (Fig.  129),  which 


T' 


M 


FIG.  120. 


is  fixed  above  the  bottom  of  an  ordinary  still.  The  head  of 
the  still  is  then  adjusted,  connection  is  made  with  a  condenser, 
and  a  current  of  steam  is  passed  in  by  the  tube  TT'T",  which 
penetrates  into  the  still.  The  steam  carries  with  it  the  essen- 
tial oil,  which  diffuses  in  it  by  virtue  of 
the  high  tension  of  the  vapor  of  these  oils  at 
100°.  The  mixed  vapors  rise  into  the  head 
of  the  still  and  condense  in  the  condensing 
worm.  The  condensed  water,  generally 
clouded  by  little  drops  of  the  essential  oil, 
is  received  in  a  vessel  of  peculiar  form, 
which  is  called  a  Florentine  receiver.  It  is 
shaped  like  an  ordinary  flask  (Fig.  130), 
having  at  its  bottom  a  tube  which  curves 
upwards,  in  the  form  of  a  swan's  neck,  and 
the  upper  part  of  which  is  but  little  below 
the  mouth  of  the  flask.  As  the  condensed  water  and  oil  collect 
in  this  ingenious  apparatus,  the  oil  separates  and  floats  on  the 
water ;  as  the  distillation  continues,  the  liquid  rises  not  only  in 


FIG.  130. 


598  ELEMENTS   OP   MODERN   CHEMISTRY. 

the  flask,  but  in  the  lateral  tube,  until  the  water,  which  is 
always  in  large  excess,  reaches  the  level  of  the  curved  neck 
and  flows  off  alone,  the  lighter  oil  accumulating  in  the  flask. 

Among  the  essential  oils  whose  composition  is  represented 
by  the  formula  C10H16,  the  most  important  is  oil  of  turpentine, 
which  is  obtained  by  distilling  the  turpentine  of  commerce  with 
water.  Turpentine  is  a  mixture  of  resin  and  essential  oil,  and 
flows  from  incisions  cut  in  the  trunks  of  trees  of  the  genera 
Pinus,  Abies,  Picea,  Larix. 

When  this  resinous  substance  is  distilled  with  water,  the  oil 
passes  over  and  the  resin  remains ;  the  latter  is  called  colo- 
phany,  or  rosin. 

Turpentine. — Bordeaux  turpentine,  which  comes  from  the 
Pinus  maritima  (Pinus  Pinaster),  yields,  by  distillation  with 
water,  an  essential  oil  which  boils  at  156°,  and  turns  the  plane 
of  polarization  to  the  left.  Density  at  0°,  0.877. 

Australine,  or  English  oil  of  turpentine,  which  comes  from 
the  Pinus  Australis,  has  the  same  boiling-point  as  the  preced- 
ing, but  turns  the  plane  of  polarization  to  the  right.  Density 
at  16°,  0.864  (Berthelot).  American  oil  of  turpentine,  derived 
from  Pinus  palustris,  is  also  dextrogyrate. 

Metamorphoses  of  Oil  of  Turpentine. — 1.  When  exposed 
to  the  air,  oil  of  turpentine  gradually  absorbs  oxygen,  becomes 
yellow  and  partly  resinified.  This  slow  oxidation  is  due  to  the 
production  of  ozone,  with  which  the  oil  becomes  charged ;  it 
then  possesses  oxidizing  properties  (page  61). 

2.  Concentrated  nitric  acid  oxidizes  oil  of  turpentine  with 
such  energy  that  the  mixture  sometimes  takes  fire.     When 
boiled    with   dilute   nitric  acid,  it   forms   teraphthalic    acid, 

rT)2IT 
C6H4<^Q2rrj  one  of  the  isomerides  of  phthalic  acid  (Cailliot). 

3.  When  a  mixture  of  alcohol,  nitric  acid,  and  oil  of  turpentine 
is  left  to  itself  for  some  time,  the  latter  substance  fixes  the  ele- 
ments of  three  molecules  of  water  and  is  converted  into  a  crys- 
tallized solid  body,  C10H2002  -f  H20,  called  terpin. 

4.  When  oil  of  turpentine  is  mixed  with  -^  its  weight  of 
concentrated  sulphuric  acid,  and  the  mixture  is  agitated,  it  is 
converted  into  an  isomeric  hydrocarbon,  terebene,  which  boils 
at  156°,  and  a  polymeric  hydrocarbon,  C20H32,  which  boils 
between  310  and  313°  (H.  Dcville).     By  reason  of  the  re- 
ducing action  which  the  oil  of  turpentine  exerts  on  the  sul- 
phuric acid,  and  which  produces  sulphurous  oxide  and  water, 


TURPENTINE.  599 

two  atoms  of  hydrogen  are  removed  from  the  molecule  C10H16, 
and,  independently  of  terebene,  a  certain  quantity  of  cymene, 
C10HU,  is  formed  (Riban). 

C10H16  -f  S04H2  =  C10HU  +  SO2  -f  2H20 

5.  The  hydracids  combine  with  oil  of  turpentine.    Three  com- 
pounds of  turpentine  and  hydrochloric  acid  are  known.    A  solid 
hydrochloride,  C10H16.HC1,  is  deposited  from  cooled  oil  of  tur- 
pentine by  the  action  of  gaseous  hydrochloric  acid,  and  is  called 
artificial  camphor.     It  is  levogyrate,  or  dextrogyrate,  accord- 
ingly as  it  has  been  prepared  from  turpentine  or  australine. 
The  crystals  are  deposited  from  a  very  acid,  colorless  liquid,  con- 
taining a  liquid  combination  of  turpentine  and  hydrochloric  acid. 

When  oil  of  turpentine  is  left  for  a  month  in  contact  with 
very  concentrated  hydrochloric  acid,  a  dihydrochloride  is 
formed,  C10H16.2HC1.  It  is  a  solid  body,  and  is  identical  or 
isomeric  with  the  artificial  camphor  of  oil  of  lemon,  obtained 
by  passing  hydrochloric  acid  gas  into  oil  of  lemon. 

6.  Antimony  trichloride  transforms  oil  of  turpentine  into  a 
solid  polymeride,  tetraturpentine. 

Terebene. — Terebene,  which  has  already  been  mentioned, 
boils  at  156°,  like  its  isomeride,  oil  of  turpentine,  from  which 
it  differs  by  being  optically  inactive ;  it  forms  no  crystalline 
hydrate  corresponding  to  terpin,  and  it  never  yields  a  dihy- 
drochloride. Like  turpentine,  it  forms  a  crystalline  monohy- 
drochloride  when  subjected  to  the  action  of  hydrochloric  acid 
gas  (Riban). 

Camphenes. — When  dextro-  or  levo-artificial  camphor  is 
heated  to  between  200  and  220°  with  sodium  stearate,  HC1 
is  removed,  and  the  camphor  is  transformed  into  a  solid,  crys- 
tallizable  hydrocarbon,  fusible  at  146°,  and  boiling  at  160°. 
It  is  camphene,  and  is  optically  active  in  the  same  direction  as 
the  hydrochloride,  from  which  it  is  derived. 

The  sodium  stearate  here  acts  as  a  feeble  alkali ;  when  it  is 
replaced  by  sodium  benzoate,  inactive  camphene  is  set  at  lib- 
erty. The  camphenes  yield  only  monohydrochlorides  by  the 
action  of  hydrochloric  acid  gas  (Berthelot). 

The  hydrochlorides  of  turpentine,  terebene,  and  camphene 
are  isomeric ;  the  first  is  almost  undecomposable  by  water  at 
100°,  the  second  loses  all  of  its  hydrochloric  acid  by  the  action 
of  boiling  water,  and  it  is  the  same  with  the  third,  which,  how- 
ever, regenerates  solid  camphene  (Riban). 


600  ELEMENTS    OF    MODERN    CHEMISTRY. 

Isoturpentine. — When  oil  of  turpentine  is  heated  to  300°, 
it  is  transformed  into  a  new  isomeride,  which  is  active  and 
levogyrate:  it  is  isoturpentine,  and  boils  towards  176°.  Den- 
sity at  0°,  0.859.  At  the  same  time  as  isoturpentine,  meta- 
turpentine  is  formed,  C^H32,  boiling  at  360°. 

Terpilene. — This  is  another  isomeride  of  oil  of  turpentine, 
and  boils  at  the  same  temperature.  It  is  obtained  by  removing 
all  of  the  hydrochloric  acid  from  the  dihydrochloride,  C10H16 
2HC1,  by  the  action  of  either  sodium  (Berthelot)  or  aniline 
(Lauth  and  Oppenheim). 

It  is  characterized  by  the  fact  that  it  yields  a  dihydrochlo- 
ride with  great  ease  by  the  action  of  gaseous  hydrochloric  acid, 
and  does  not  form  a  monohydrochloride. 

Citrene,  C10H16. — This  hydrocarbon  is  contained  in  oil  of 
lemon,  together  with  an  oxygenized  body.  It  is  a  colorless 
liquid,  having  an  agreeable  odor.  It  boils  at  173-174°.  Den- 
sity at  15°,  0.85. 

Citrene  unites  readily  with  hydrochloric  acid,  producing  a 
crystalline  dihydrochloride  of  citrene.  C10H16.2HC1,  fusible  at 
14°. 

ORDINARY  CAMPHOR,  OR  LAUREL  CAMPHOR. 


Camphor  exists  in  all  of  the  organs  of  the  Laurus  camphora, 
a  tree  of  China,  Japan,  and  the  islands  of  the  Bay  of  Sundy. 
When  the  wood  is  chipped  and  distilled  with  water,  the  cam- 
phor volatilizes  and  condenses  in  rice-straw,  with  which  the 
heads  of  the  stills  in  which  the  operation  is  conducted  are  filled. 
The  product  thus  obtained  in  the  form  of  small  crystals  is  re- 
fined by  sublimation  in  glass  vessels  heated  on  a  sand-bath. 

A  camphor  identical  with  laurel  camphor  is  deposited  from 
the  oil  of  Matricaria  parthenium  when  the  latter  is  cooled. 
It  is  matricaria  camphor. 

Camphor  forms  a  semi-transparent,  crystalline  mass.  Its 
odor  is  strong  and  aromatic ;  its  taste,  bitter  and  burning.  It 
melts  at  175°,  and  boils  and  distils  without  alteration  at  204°. 
Its  density  at  0°  is  1.0.  At  ordinary  temperatures,  the  ten- 
sion of  its  vapor  is  so  great  that  it  sublimes  spontaneously  in 
the  vessels  in  which  it  is  kept. 

Camphor  is  almost  insoluble  in  water;    when  thrown  in 


CAMPHOR.  601 

small  fragments  on  the  surface  of  that  liquid,  it  executes  gyra- 
tory movements.  It  dissolves  in  alcohol  and  ether,  and  the  al- 
coholic solution  rotates  the  plane  of  polarization  to  the  right. 

Camphor  is  inflammable,  and  burns  with  a  smoky  flame. 
The  following  are  its  principal  reactions : 

1.  When  heated  with  phosphoric  anhydride,  or  with  chloride 
of  zinc,  it  loses  the  elements  of  water  and  is  converted  into  a 
hydrocarbon  called  cymene. 

C10H160   =    H2Q    _|_    C10HH 

Camphor.  Cymene. 

2.  Camphor  appears  to  be  an  aldehyde.     Although  it  does 
not  fix  hydrogen  directly,  it  can  nevertheless  be  converted  into 
a  compound,  C10H180,  which  is  borneol,  or  Borneo  camphor. 
This  is  accomplished  by  the  action  of  sodium,  which  replaces 
the  hydrogen  of  a  portion  of  the  camphor,  forming  a  sodium- 
camphor,  while  the  displaced  hydrogen  is  fixed  upon  another 
portion  of  camphor  (Baubigny). 

According  to  this  reaction,  corroborated  by  the  inverse  re- 
action, which  will  be  indicated  farther  on,  the  same  relations 
seem  to  exist  between  borneol  and  camphor  as  between  alco- 
hol and  aldehyde. 

C2H40  C2H6O 

Aldel.y.Ie.  Alcohol. 

C10H16Q  C10H180 

Camphor.  Borneol. 

3.  When  camphor  is  heated  for  a  long  time  with  an  alcoholic 
solution  of  potassium  hydrate,  it  is  decomposed  into  an  acid 
and  an  alcohol,  which  is  borneol  (Berthelot). 

2C10H160     +    KOH    =     C10H15K02     -f     C10H180 

Camphor.  Potassium  camphate.  Borneol. 

4.  When  vapor  of  camphor  is  passed  over  soda-lime,  heated 
to  about  300°,  the  sodium  salt  of  campholic  acid  is  obtained 
(Delalande). 

CioHi6O     +     NaOH     _     cioH17Na02 

Camphor.  Sodium  campholate. 

5.  When  camphor  is  subjected  to  the  action  of  aqueous 
hypochlorous  acid,  it  is  converted    into  monochloro-camphor, 
C10H15C10,    which    constitutes    a   colorless,    crystalline    mass, 
slightly  soluble  in  water,  freely  soluble  in  alcohol  and  ether, 
and  fusible  at  95°. 

2A  51 


602  ELEMENTS   OF   MODERN    CHEMISTRY. 

6.  By  the  action  of  bromine  on  camphor  at  100  or  120°, 
monobromo  -  camphor,    C10H15BrO,    and    dibromo  -  camphor, 
C10H14Br2O,  are  formed.     These  bodies  crystallize  in  colorless 
prisms.     The  first  fuses  at  76°,  the  second,  at  114°. 

A  bromide  of  camphor,  C10H16OBr2,  is  also  known;  it  is 
formed  by  the  action  of  bromine  on  a  solution  of  camphor  in 
chloroform.  It  is  a  crystalline  body  which  decomposes  spon- 
taneously, especially  by  the  action  of  light,  losing  hydrobromic 
acid  and  being  converted  into  monobromo-camphor. 

7.  Camphor  absorbs  hydrochloric  acid  gas,  forming  an  oil 
which  is  instantly  decomposed  by  water,  regenerating  camphor. 
Cold  nitric  acid  dissolves  it,  forming  an  oily  liquid  which  is  de- 
composed by  water,  camphor  being  precipitated. 

8.  When  camphor  is  boiled  with  nitric  acid,  it  is  oxidized 
and  converted  into  camphoric  acid. 

CioHi60     _j_     03     =     cioH1604 

Camphor.  Camphoric  acid. 

BORNEOL,  OR  BORNEO  CAMPHOR. 

C10H18O 

This  camphor  is  extracted  from  the  Dryobalanops  aromatica, 
a  tree  which  grows  in  the  Sundy  Islands.  Berthelot  has  ob- 
tained it  by  the  action  of  an  alcoholic  solution  of  potassa  on 
ordinary  camphor.  It  occurs  in  small,  colorless,  transparent, 
and  friable  crystals.  Its  odor  recalls  at  the  same  time  that  of 
camphor  and  that  of  pepper.  Its  taste  is  burning.  It  melts 
at  198°,  and  boils  at  212°.  It  turns  the  plane  of  polarization 
to  the  right.  It  is  insoluble  in  water,  but  dissolves  readily  in 
alcohol  and  in  ether.  When  treated  with  cold,  fuming  nitric  acid, 
it  loses  H2,  and  is  converted  into  ordinary  camphor,  C10H160. 

BENZOL. 

C6H« 

This  important  body  was  discovered  in  1825  by  Faraday. 
Mitscherlich  obtained  it  by  heating  benzoic  acid  with  an  excess 
of  lime. 

C7H602     ==     CO2     +     C6H6 

Benzoic  acid.  Benzol. 

It  is  now  obtained  in  large  quantities  from  coal-tar  by  dis- 
tilling the  latter  body.  The  more  volatile  products  contain  the 


BENZOL.  603 

benzol,  which  is  purified  by  fractional  distillation.  That  which 
passes  below  85°  is  principally  benzol,  and  the  latter  crystal- 
lizes out  when  the  liquid  which  passes  between  80  and  85°  is 
cooled  to  — 5°.  The  crystals  are  collected  and  separated  by 
expression  from  the  product  remaining  liquid.  They  constitute 
pure  benzol.*  Berthelot  has  recently  made  the  direct  synthesis 
of  benzol  by  exposing  acetylene  to  a  temperature  near  redness. 
3C2H2  =  C6H6 

Acetylene.  Benzol. 

Benzol  is  a  colorless,  strongly  refracting  liquid.  At  0°,  it 
solidifies  to  crystals  which  melt  at  5.5°.  It  boils  at  80.5°. 
It  is  insoluble  in  water,  but  dissolves  in  alcohol  and  ether.  It 
is  inflammable,  and  burns  with  a  bright,  smoky  flame. 

When  long  agitated  with  fuming,  or  even  ordinary  sulphuric 
acid,  it  dissolves,  forming  phenylsulphurous  acid. 

C6H6        +         JpgQ*        =        JJ2Q         +-       C6H5g03H 

Phenylsulphurons  acid. 

When  heated  to  275  or  280°  for  twenty-four  hours  with  80 
to  100  parts  of  concentrated  hydriodic  acid,  benzol  is  converted 
into  hexane,  C6HU,  iodine  being  set  free. 

Action  of  Chlorine  and  Bromine  on  Benzol. — In  sun- 
light, benzol  can  absorb  directly  six  atoms  of  chlorine,  forming 
benzol  hexachloride,  C6H6C16,  crystallizable  in  brilliant  plates. 
Another  product  of  the  action  of  chlorine  on  benzol  is  mono- 
chlorobenzol,  C6H5C1,  a  liquid,  boiling  between  135  and  137°. 

An  excess  of  bromine  in  sunlight  converts  benzol  into  a  solid 
bromide,  C6H6Br6. 

Monobromobenzol,  C6H5Br,  may  be  made  by  mixing  benzol 
and  bromine  in  the  proportion  of  one  molecule  of  the  first  to 
two  atoms  of  the  second,  and  leaving  the  mixture  to  itself  for 
a  week  at  the  ordinary  temperature.  It  is  then  washed,  first 
with  water  then  with  potassa,  and  distilled.  Monobromobenzol 
boils  at  152-154°.  When  heated  with  sodium,  it  yields  to  the 

C6H5 

latter  its  bromine,  and  a  hydrocarbon  C12H10  =  i      .,  called 

C  MD 
diphenyl,  is  obtained. 

Dibromobenzol,  C6H4Br2,  is  readily  formed  by  the  action  of 
an  excess  of  bromine  on  benzol.  It  crystallizes  in  beautiful 
prisms,  fusible  at  89°.  It  boils  at  219°. 

#  Benzol  must  not  be  confounded  with  the  benzine  derived  from  petro- 
leum, which  is  a  saturated  hydrocarbon. 


604  ELEMENTS    OF    MODERN    CHEMISTRY. 

Nitrobenzol,  C6H3(N02). — If  benzol  be  poured  in  small 
portions  into  monohydrated  nitric  acid,  and  water  be  added  to 
the  mixture,  an  oily,  yellow  liquid  separates,  constituting  nitro- 
benzol. 

C6H6  +  HNO3  =  H20  +  C6H5(N02) 

It  is  benzol  in  which  one  hydrogen  atom  is  replaced  by  the 
group  (NO2)'. 

Nitrobenzol  is  a  yellowish  liquid,  having  a  strong  odor  of 
bitter  almonds.  It  boils  at  205°,  and  solidifies  at  3°.  It  is 
employed  in  perfumery  under  the  name  essence  of  Mirbane. 

By  the  action  of  reducing  agents,  such  as  hydrogen  sulphide, 
ammonium  sulphide,  tin  and  hydrochloric  acid,  or  iron-filings 
and  acetic  acid,  nitrobenzol  is  converted  into  aniline  or  phenyl- 
arnine. 

C6H5(N02)     +     3H2    =     2H20     -f     C6H5(NH2) 

Nitrobenzol.  Aniline. 

When  long  heated  with  very  concentrated  nitric  acid,  nitro- 
benzol is  transformed  into  metadinitrobenzol,  C6H4(N02)2,  which 
forms  long,  right  rhombic  prisms,  fusible  at  118°. 

Azoxybenzol,  Azobenzol,  Hydrazobenzol, — There  are  other 
products  of  the  reduction  of  nitrobenzol,  independently  of 
aniline.  When  nitrobenzol  is  acted  upon  by  alcoholic  potas- 
sium hydrate,  or  by  sodium  amalgam  in  presence  of  water,  the 
reduction  is  less  complete,  and  it  is  converted  successively  into 
azoxybenzol  and  azobenzol  (Zinin). 

2C6H5-NQ2     +     3H2    =    3H2Q     + 

Nitrobenzol.  Azoxybenzol. 

2C6H5-N02     +     4H2    =    4H2Q       +      ^ 

C6H5-N 
Nitrobenzol.  Azobenzol. 

Azoxybenzol  forms  long,  yellow  prisms,  fusible  at  36°,  very 
soluble  in  alcohol  and  ether. 

Azobenzol  forms  large,  red  crystals,  fusible  at  66.5°.  It 
boils  without  decomposition  at  293°.  It  is  insoluble  in  water, 
but  dissolves  in  alcohol  and  ether. 

In  the  presence  of  reducing  agents,  such  as  hydrogen  sul- 
phide, ammonium  sulphide,  or  sodium  amalgam  and  water, 
both  of  the  preceding  bodies  fix  hydrogen  and  are  converted 
into  hydrazobenzol. 


GYANOBENZOL  —  PHENOL.  605 

C6H5-N 


C6H5-N 

Azobenzol.  Hydrazobenzol. 

The  latter  body  crystallizes  in  tables,  fusible  at  131°,  almost 
insoluble  in  water  but  soluble  in  alcohol  and  ether.  When 
submitted  to  dry  distillation,  it  breaks  up  into  azobenzol  and 
aniline. 

2Ci2Hi2N2    =    ci2Hl°N2     +     2C6H5.NH2 

Hydrazobenzol.  Azobenzol.  Aniline. 

CYANOBENZOL. 

(PHENYL   CYANIDE,  BENZONITRILE.) 


This  body  is  formed  in  various  reactions,  particularly  in  the 
destructive  distillation  of  hippuric  acid,  and  by  the  dehydration 
of  benzamide  by  phosphoric  anhydride. 

C6H5-CO.NH2    —    H20    =     C6H5-CN 

Benzamide.  Benzonitrile. 

It  is  a  colorless  oil,  which  boils  at  191°.  When  heated  with 
the  alkalies,  it  yields  benzoic  acid  and  ammonia. 

C6H5-CN     +     2H20    =    C6H5-C02H     +     NH3 

Benzonitrile.  Benzoic  acid. 

PHENOL,  OR  PHENYL  HYDRATE. 


This  body  bears  the  same  relation  to  benzol  that  wood-spirit 
does  to  marsh  gas. 

CH*  CH3.OH 

Methane.  Methyl  hydrate. 

C6H6  CPIP.OH 

Benzol.  Phenol. 

It  was  discovered  in  coal-tar  by  Runge,  who  named  it  car- 
bolic acid.  Laurent  demonstrated  that  it  plays  the  part  of  an 
alcohol.  Indeed,  it  presents  points  of  resemblance  with  the 
monatomic  alcohols,  but  it  differs  from  them  by  its  acid  char- 
acter, on  account  of  which  it  is  sometimes  called  phenic  a,cid. 

Preparation.  —  Large  quantities  of  phenol  are  obtained  from 
coal-tar,  from  which  it  is  separated  by  distillation.  That  part 
which  passes  between  150  and  200°  is  collected  apart  and 

51* 


606  ELEMENTS   OF   MODERN    CHEMISTRY. 

mixed  with  a  saturated  solution  of  potassium  or  sodium  hy- 
drate to  which  solid  potassa  or  soda  is  added.  A  crystalline 
phenate  of  potassium  or  sodium  is  formed ;  it  is  dissolved  in 
boiling  water,  the  insoluble  oil  which  floats  is  separated,  and 
the  alkaline  solution  is  neutralized  with  hydrochloric  acid. 
The  phenol  separates ;  it  is  washed  with  a  small  quantity  of 
water,  dehydrated  with  calcium  chloride,  and  rectified.  The 
distilled  product  is  cooled  to — 10°,  and  the  crystals  which  are 
deposited  are  allowed  to  drain  out  of  contact  with  the  air. 

Phenol  may  be  made  artificially  from  benzol  by  a  process 
which  is  applicable  to  the  preparation  of  all  the  phenols.  It 
consists  in  treating  benzol  with  fuming  or  even  ordinary 
sulphuric  acid.  Phenylsulphurous  acid  is  formed ;  this  is 
diluted  with  water  to  separate  the  excess  of  hydrocarbon,  and 
the  solution  is  neutralized  with  chalk  ;  calcium  phenylsulphite, 
which  is  soluble,  and  sulphate,  which  is  insoluble,  are  formed. 
The  calcium  phenylsulphite  is  converted  into  sodium  phenyl- 
sulphite by  double  decomposition  with  sodium  carbonate,  and 
after  evaporation  and  desiccation,  the  sodium  phenylsulphite  is 
fused  in  a  silver  crucible  with  an  excess  of  potassium  hydrate. 
The  mass  is  exhausted  with  water,  and  the  alkaline  solution  is 
decomposed  by  hydrochloric  acid.  The  phenol  separates  and 
is  dried  and  purified  by  distillation  (Dusart,  Wurtz,  Kekule). 

The  decomposition  of  sodium  or  potassium  phenylsulphite 
is  expressed  in  the  following  equation : 

C6H5.S03K     +     KOH    =     C6H5.OH     +     K2S03 

Potassium  phenylsulphite.  Phenol.  Potassium  sulphite. 

There  is  another  very  simple  synthesis  of  phenol.  In  pres- 
ence of  aluminium  chloride,  benzol  absorbs  oxygen  directly  and 
phenol  is  formed. 

C6H6  +  0  =  C6H6O 

This  reaction  is  one  of  the  most  unexpected  and  most  in- 
teresting applications  of  a  general  method  of  synthesis  discov- 
ered by  Friedel  and  Crafts  (see  page  619). 

Properties  of  Phenol. — Phenol  is  a  solid,  crystallizing  in 
long,  colorless  needles,  fusible  at  35°.  It  has  a  peculiar,  char- 
acteristic odor,  and  an  acrid,  burning  taste.  It  boils  at  186°. 
It  is  slightly  soluble  in  water,  but  dissolves  readily  in  concen- 
trated acetic  acid.  It  possesses  antiseptic  properties. 

Although  phenol  is  neutral  to  litmus-paper,  it  forms  definite 
combinations  with  the  alkalies.  When  it  is  mixed  with  a  very 


TRINITROPHENOL.  607 

concentrated  solution  of  potassium  hydrate,  a  crystalline  mass 
is  obtained  which  constitutes  potassium  phenate,  C6H5.OK. 

Phosphorus  perchloride  converts  it  into  phenyl  chloride, 
identical  with  monochlorobenzol. 

C6H5.OH     +     PGP     =     C6H5C1     +     POOP     +     HC1 

Phenol.  Phenyl  chloride. 

The  following  remarkable  reaction  of  phenol  was  first  noticed 
by  Reimer  and  Tiemann.  When  it  is  heated  with  chloroform 
and  an  excess  of  sodium  hydrate,  in  the  proportion  of  one 
molecule  each  of  phenol  and  chloroform  and  four  molecules  of 
alkali,  it  is  converted  into  salicylic  aldehyde  (salicyl  hydride). 

C6H5.ONa  +  SNaOH  +  CHCP=  C7H502Na  -f  3NaCl  +  2H2O 

Sodium  Sodium  salicylite. 

phenate. 

The  compound  C7H502Na  is  the  sodium  compound  of  sali- 
cylic aldehyde,  into  which  it  is  converted  by  hydrochloric  acid. 

TRINITROPHENOL. 

(PICRIC  ACID.) 
C6H2(NO2)3.OH 

When  phenol  is  boiled  with  concentrated  nitric  acid,  it  is 
converted  into  trinitrophenol. 

C6H5.OH  -f  3HN03  =  3H20  +  C6H2(N02)3.OH 

This  body  has  long  been  known,  and  is  generally  called  picric 
acid.  It  deposits  from  boiling  water  in  lemon-yellow,  crystal- 
line plates,  only  slightly  soluble  in  cold  water.  Its  taste  is  very 
bitter.  With  the  bases  it  forms  crystallizable  salts,  which  deto- 
nate with  violence  when  heated. 

Potassium  pier  ate,  C6H2(N02)3.OK,  crystallizes  in  long,  yel- 
low needles,  soluble  in  14  parts  of  boiling  water  and  in  250 
parts  at  15°.  It  explodes  violently  when  heated. 

Picramic  Acid.  —  When  a  current  of  hydrogen  sulphide  is 
passed  through  an  alcoholic  solution  of  picric  acid  saturated 
with  ammonia,  sulphur  separates  and  the  picric  acid  is  con- 
verted into  picramic  acid  (A.  Girard). 


3H2S  =  2H20  +  S»  +  C«H2(NO2)2(NH2)OH 

Picric  acid.  Picramic  acid. 

The  hydrogen  sulphide  partially  reduces  the  picric  acid,  and 
one  of  the  three  groups  (NO2)  is  thus  converted  into  a  group 


608  ELEMENTS   OP   MODERN   CHEMISTRY. 

(NH2).  Picramic  acid  is  dinitro-amido-phenol,  that  is,  phenol 
in  which  two  atoms  of  hydrogen  are  replaced  by  two  groups 
(NO2),  and  a  third  atom  of  hydrogen  by  the  group  NH2. 

When  acetic  acid  is  added  to  a  hot  aqueous  solution  of  the 
ammonium  salt  of  picramic  acid,  the  picramic  acid  is  deposited 
in  fine  red  needles. 

AUKIN   (ROSOLIC   ACIDS). 

When  1£  part  of  phenol  is  heated  with  1  part  of  oxalic 
acid  and  2  parts  of  sulphuric  acid,  it  is  converted  into  a  color- 
ing-matter, which  was  first  described  under  the  name  rosolic 
acid,  or  coralline-yellow.  The  same  body  or  analogous  bodies 
may  be  obtained  by  means  of  the  rosanilines  (see  farther  on). 
Indeed,  it  has  been  recognized  that  there  are  several  homolo- 
gous bodies  having  the  properties  and  the  constitution  of  roso- 
lic acid. 

Rosolic  acid  made  from  pure  phenol  contains  C19H1403,  and 
is  called  aurin  (Dale  and  Schorlemmer).  It  occurs  in  very 
brilliant,  red,  anorthic  prisms  having  a  blue  or  green  reflection. 
It  corresponds  to  a  rosaniline,  C19Hn(NH2)3  (pararosaniline). 

To  ordinary  rosaniline  and  its  superior  homologue,  chrysoto- 
luidine  (see  farther  on),  correspond  two  other  rosolic  acids,  supe- 
rior homologues  of  aurin.  The  following  formulas  indicate  the 
relations  which  exist  between  these  bodies: 

ClflH"(OH)3  C19Hn(NH2)3 

Aurin.  Inferior  homologue  of  rosaniline. 

C20H13(OH)3  C20H13(NH2)3 

Rosolic  acid.  Ordinary  rosaniline. 

Aurin  is  used  in  dyeing.  When  it  is  heated  to  180°  with 
an  alcoholic  solution  of  ammonia,  it  is  converted  into  a  bright- 
red  coloring  matter,  noticed  by  Persoz,  and  employed  in  dyeing 
under  the  name  coralline-red. 


ANILINE,  OR   PHENYLAMINE. 


Aniline  was  discovered  by  Unverdorben  among  the  products 
of  the  distillation  of  indigo,  and  was  extracted  from  coal-tar  by 
Runge.  It  is  now  prepared  artificially  by  a  process  discovered 
by  Zinin.  This  process  consists  in  converting  benzol  into  ni- 


ANILIDES.  609 

trobenzol,  and  subjecting  the  latter  to  the  action  of  reducing 
agents  (see  nitrobenzol). 

Iron  and  acetic  acid  are  advantageously  used  to  accomplish 
this  reduction  (Bechamp). 

Aniline  is  a  colorless,  mobile,  highly-refracting  liquid,  having 
a  peculiar,  unpleasant  smell,  and  an  acrid,  burning  taste.  It 
is  a  little  heavier  than  water.  It  boils  at  184.8°.  When  ex- 
posed to  the  air,  it  becomes  brown  and  is  eventually  resinified. 

"Aniline  is  almost  insoluble  in  water,  but  mixes  in  all  pro- 
portions with  alcohol,  ether,  and  the  fatty  and  volatile  oils. 

It  does  not  restore  the  blue  color  to  reddened  litmus-paper, 
but  nevertheless  possesses  the  character  of  an  alkaloid,  for  it 
forms  well-defined  salts  with  the  acids. 

Reactions. — 1.  If  a  nitrate  and  sulphuric  acid  be  added  to 
aniline,  a  red  color  is  produced. 

2.  If  a  few  drops  of  aniline  be  poured  into  an  excess  of  sul- 
phuric acid,  and  a  small  quantity  of  potassium  dichromate  be 
added,  a  magnificent  blue  color  is  developed,  which  changes  to 
violet  on  the  addition  of  water. 

3.  A  solution  of  calcium  hypochlorite  (chloride  of  lime) 
added  to  aniline  produces  a  beautiful  violet  tint. 

4.  When  a  solution  of  an  aniline  salt  is  heated  with  cupric 
chlorate,  an  intense  black  color  is  developed  (Ch.  Lauth). 

These  reactions  are  applied  in  the  arts  in  the  preparation  of 
coloring  matters  of  incomparable  richness.  The  most  impor- 
tant of  these  matters  is  rosaniline,  or  fuchsine,  which  will  be 
described  farther  on. 

Salts  of  Aniline. — These  are  obtained  by  saturating  aniline 
by  the  acids. 

Aniline  liydrochloride,  C6H7N.HC1,  forms  colorless  needles, 
which  are  fusible,  and  can  be  distilled  without  alteration  ;  they 
are  very  soluble  in  water  and  in  alcohol.  Platinic  chloride  pre- 
cipitates from  the  solution  fine  yellow  needles  of  a  chloro-plati- 
nate,  (^H'N.HCl/PtCl4. 

Aniline  oxalate,  (C6H7N)2C2H204,  crystallizes  from  water  in 
hard,  thick  prisms.  When  heated,  it  loses  the  elements  of 
water,  and  is  converted  into  oxanilide. 

ANILIDES. 

By  the  action  of  heat,  the  aniline  salts  lose  the  elements  of 
water,  and  form  compounds  analogous  to  the  amides,  and  which 

2.Y* 


610  ELEMENTS   OF   MODERN    CHEMISTRY. 

Gerhardt  named  anilides.  When  aniline  oxalate  is  heated,  it 
is  converted  into  oxanilide,  which  is  no  other  than  oxamide 
in  which  two  atoms  of  hydrogen  ara  replaced  by  two  phenyl 
groups,  (C6H5). 

C2Q2)  C2Q2) 

H2  \  N2  (C«H^2      ^2 

H2J  H2j 

Oxamide.  Phenyl  oxamide  (oxanilide). 


H  V  N  C«H5    N 

Hj  HJ 

Acetamide.  Pheny  lace  tarn  ido  (acetanilide.) 


DIAZOBENZOL  COMPOUNDS. 

Nitrous  acid  exerts  an  energetic  action  upon  aniline  and  the 
analogous  bases ;  it  is  indicated  here  because  it  presents  a  great 
generality  and  gives  rise  to  remarkable  bodies,  which  are  called 
diazo-compounds. 

When  a  current  of  nitrous  gas  is  passed  into  a  saturated  so- 
lution of  an  aniline  salt,  such  as  the  nitrate,  crystals  of  diazo- 
benzol nitrate  are  deposited. 

C6H7N.HN03    +     HNO2    =    2H2O     +     C6H5N2.N03 

Aniline  nitrate.  Diazobenzol  nitrate. 

This  body  is  formed  by  the  substitution  of  one  atom  of  nitro- 
gen for  three  atoms  of  hydrogen  in  aniline  nitrate. 

C«H8-NH».HNOS    aniline  nitrate. 
C«H5-N=N-(N03)  diazobenzol  nitrate. 

It  forms  long,  colorless  prisms,  very  soluble  in  water,  slightly 
soluble  in  alcohol,  and  insoluble  in  ether.  It  explodes  violently 
by  heat  or  by  percussion.  This  salt  and  its  congeners  present 
two  remarkable  reactions.  When  heated  with  water,  they  dis- 
engage nitrogen,  and  are  converted  into  phenols. 

CeH5N2  NOs  ^_  H20  =  c*H5.OH  -f  N2  +  HNO3 

When  they  are  boiled  with  absolute  alcohol,  they  are  reduced 
to  hydrocarbons,  nitrogen  being  disengaged  and  the  alcohol 
being  transformed  into  aldehyde. 

OTPN'.HSO*  +  C2H60  =  C2H40  +  C6H6  +  N2  -f  H2S04 

Diazobenzol  sulphate.  Aldehyde.         Benzol. 

When  aniline  is  added  to  an  aqueous  solution  of  diazobenzol 


ROSANILINE.  611 

nitrate,  a  diazo-compound  is  obtained  which  is  more  complex 
than  the  preceding  and  is  called  diazoamidobenzoL 


+  NH2.C6H5  =  C6IP-N2-NH.C6H5  +  HNO3 

Diazobenzol  nitrate.  Aniline.  DiazoamidobenzoL 

The  same  body  is  formed  when  a  current  of  nitrogen  tri- 
oxide  is  passed  into  a  cooled  alcoholic  solution  of  aniline.  It 
forms  brilliant,  golden-yellow  scales,  fusible  at  91°.  It  ex- 
plodes at  a  higher  temperature. 


ROSANILINE  AND  ITS  DERIVATIVES. 


This  magnificent  red  coloring  matter  is  obtained  by  heating 
aniline  to  150  or  160°  with  arsenic  acid,  which  acts  in  this  case 
as  an  oxidizing  agent.  The  solid  product  of  the  reaction  is 
dissolved  in  water,  and  the  filtered  solution  is  treated  with  solu- 
tion of  sodium  hydrate  ;  the  rosaniline  which  was  combined 
with  arsenic  acid  is  precipitated.  It  is  then  dissolved  in  acetic 
or  hydrochloric  acid,  and  the  salt  so  formed  is  crystallized. 
It  separates  in  magnificent  crystals  which  present  a  green  re- 
flection, like  the  scales  of  cantharides,  and  dissolve  in  alcohol 
with  a  rich  purple  color. 

The  rosaniline  formed  in  this  reaction  results  from  the  oxida- 
tion of  the  aniline,  and  toluidine  (see  farther  on),  which  always 
exists  in  commercial  aniline. 

C6H7N  +  2C7H9N  +  O3  =  C20H19N3  +  3H20 

Aniline.  Toluidine.  Rosaniline. 

In  the  preparation  of  rosaniline,  arsenic  acid,  the  use  of 
which  is  dangerous,  has  been  replaced  by  another  oxidizing 
agent,  which  is  nitrobenzol.  The  latter  acts  by  virtue  of  the 
group  NO2,  which  it  contains  (J.  Persoz).  This  improvement 
has  been  introduced  in  France  by  Coupier,  and  in  Germany  by 
Meister,  Lucius,  Bruning. 

Properties  of  Rosaniline.  —  The  methods  of  preparation 
just  indicated  furnish  the  salts  of  rosaniline,  such  as  the  hydro- 
chloride,  which  is  the  rich  coloring  matter  known  as  fuchsine. 
The  free  base  is  obtained  by  treating  a  hot,  saturated  solution 
of  the  hydrochloride  with  an  excess  of  soda.  The  rosaniline 
separates  as  an  almost  colorless,  crystalline  precipitate.  It  is  a 
triacid  base  which  requires  three  molecules  of  hydrochloric 


612  ELEMENTS    OF    MODERN   CHEMISTRY. 

acid  for  its  saturation.  It  is  curious  that  free  rosaniline  is 
colorless  and  occurs  in  small  crystals. 

The  monohydrochloride  of  rosaniline,  C20H19N3.HC1  (fuch- 
sine),  forms  dark-colored,  rhombic  tables,  having  a  splendid 
green  reflection.  It  is  but  slightly  soluble  in  water,  but  dis- 
solves readily  in  alcohol,  forming  an  intense  purple  solution. 

The  trihydrochloride,  C20H19N3.3HC1,  forms  yellow-brown 
needles  which  lose  hydrochloric  acid  when  heated  or  when  dis- 
solved in  water. 

Rosaniline  and  its  salts  present  two  important  reactions  : 

1.  When  a  salt  of  rosaniline  is  treated  with  reducing  agents, 
such  as  nascent  hydrogen  (zinc  and   hydrochloric  acid),  the 
base  fixes  two  atoms  of  hydrogen  and  is  converted  into  leu- 
caniline,  C20H21N3,  a  white  powder  slightly  soluble  in  water. 

2.  By  the  action  of  nitrogen  trioxide,  rosaniline  is  converted 
into  a  diazo-derivative  which  yields  rosolic  acid  when  boiled 
with  water  (pages  608  and  610). 

Constitution  of  Rosaniline,  —  According  to  Hofmann,  the 
formula  C20HI9N3  represents  the  composition  of  rosaniline.  It 
is  exact,  but  it  has  been  recognized  that  the  products  known 
under  the  name  fuchsine  contain  several  isomerides  (Rosen- 
stiehl),  and  it  is  known,  besides,  that  there  are  several  homo- 
logues  of  rosaniline.  Without  dwelling  on  the  subject,  we  may 
mention  the  following  bodies  : 

C19H"N3  pararosaniline  (Fischer). 
C20fli9N3  rosaniline. 
C21H21N3  chrysotoluidine. 

There  exist  also  corresponding  leucanilines  containing  two 
more  atoms  of  hydrogen. 

Hofmann  has  attributed  to  the  rosaniline  C20H19N3  the  con- 
stitution expressed  by  the  formula 


2(C7H6)"  V  N3 
H3j 

According  to  him,  it  is  a  triamine,  containing  at  the  same 
time  a  diatomic  group  phenylene,  C6H*,  and  two  diatomic 
groups  C7H6. 

Recent  researches  tend  to  modify  this  view.  E.  and  0. 
Fischer  consider  that  this  rosaniline  is  a  triamine,  C20H13 
(NH2)3,  derived  from  a  hydrocarbon  C20H16,  and  that  para- 


ROSANILINE.  613 

rosaniline  is  a  triamine,  C19Hn(NH2)3,  derived  from  a  hydro- 
carbon, C19HU.  By  subjecting  the  corresponding  leucanilines 
to  the  action  of  nitrous  anhydride,  and  reducing  the  diazo- 
compounds  thus  formed  by  alcohol,  these  chemists  obtained 
the  hydrocarbons  C20H18  and  C19H16,  which  were  again  con- 
verted into  leucanilines,  and  then,  by  oxidation  of  the  latter, 
into  rosanilines. 

We  may  add  that  the  hydrocarbon  C19H16,  which  is  solid 
and  fusible  at  93°,  is  triphenylmethane,  that  is,  marsh-gas,  in 
which  three  atoms  of  hydrogen  are  replaced  by  three  phenyl 
groups. 

CH4  CH(C6H5)3 

Methane.  Triphenylmethane. 

Coloring  Matters  derived  from  Rosaniline.  —  When  rosan- 
iline is  heated  with  ethyl  iodide,  three  atoms  of  hydrogen  are 
replaced  by  three  ethyl  groups,  and  this  triethyl-rosamlme 
yields  with  the  acids  a  magnificent  violet  color,  known  as  Hof- 
mann's  violet. 

Triphenyl-rosaniline,  in  which  three  atoms  of  hydrogen  are 
replaced  by  three  phenyl  groups,  C6H5,  is  formed  when  rosani- 
line is  heated  with  an  excess  of  aniline.  This  reaction,  in 
which  ammonia  is  disengaged,  was  discovered  by  Girard  and 
de  Laire. 


_|_  3CTP.NH2  =  C20H16(C6H5)3N3  +  3NH3 

Rosaniline.  Aniline.  Triphenyl-rosaniline. 

The  hydrochloride  of  triphenyl-rosaniline  is  of  a  magnificent 
blue  color,  and  is  known  as  Lyons  blue  (Ch.  Girard  and  de 
Laire).  The  following  formulae  show  the  interesting  relations 
which  exist  between  rosaniline  and  its  ethyl  and  phenyl  deriv- 
atives : 


C20H16(C2H5)3N3         C20H16(C6H5)3N3 

Rosanilhie.  Triethyl-rosaniline.  Triphenyl-rosaniline. 

(Base  of  Hofinann's  violet.)  (Base  of  Lyons  blue.) 

We  may  mention  among  the  derivatives  of  rosaniline,  Paris 
violet  and  the  aniline  greens,  particularly  the  beautiful  color- 
ing matter  known  as  night-green,  because  it  retains  its  rich 
green  tint  in  artificial  light. 

Paris  violet,  which  has  been  for  some  years  manufactured 
by  Poirrier,  is  a  splendid  color,  produced  by  the  oxidation  of 
methylaniline  or  dimethylaniline. 

52 


614  ELEMENTS   OP   MODERN    CHEMISTRY. 


CH3VN  CH8>N 

HJ  CH3J 

Methylaniline.  Dimethylaniline. 

Ch.  Lauth  realizes  this  oxidation,  or  rather  dehydrogena- 
tion,  by  heating  methylaniline  with  cupric  chloride.  The 
reaction  is  complex,  and,  according  to  Hofmann  and  Martius, 
gives  rise  to  trimethyl-rosaniline. 

When  heated  with  methyl  chloride,  the  base  of  Paris  violet 
fixes  two  molecules  of  that  compound,  forming  a  combination 
of  trimethyl-rosaniline  and  methyl  chloride.  This  combination 
constitutes  night-green. 


Dichlorometliylate  of  trimetliyl-rosauiline 
(night-green). 

DIPHENYLAMINE. 


C«H5) 
C«H5  I  N 
HJ 


This  body  is  derived  from  ammonia  by  the  substitution  of 
two  phenyl  groups  for  two  atoms  of  hydrogen.  It  is  formed 
in  various  reactions,  of  which  the  most  interesting  was  discov- 
ered by  Girard  and  de  Laire.  It  consists  in  heating  aniline 
hydrochloride  to  256°  with  aniline.  Ammonia  is  disengaged, 
and  diphenylamine  hydrochloride  is  formed. 


H    N.HC1    +         H    N    —     C6R5    N.HC1    +    NR3 
HJ  Hj  Hj 

Free  diphenylamine  forms  crystals  fusible  at  54°.  It  boils 
at  310°.  It  is  insoluble  in  water,  but  dissolves  in  alcohol, 
ether,  benzol,  and  petroleum.  Its  odor  recalls  that  of  oil  of 
rose. 

When  heated  with  a  mixture  of  oxalic  and  sulphuric  acids, 
it  yields  a  splendid  blue  color,  soluble  in  water,  and  known  as 
diphenylamine  blue  (Girard  and  de  Laire). 

OXYPHENOLS. 

C6H6Q2 

Three  isomeric  bodies  having  the  composition  C6H602  — 

O1T 

are  known  ;  they  are  derived  from  benzol  by  the 


substitution  of  two  hydroxyl  groups  for  two  atoms  of  hydro- 


RESORCIN.  615 

gen.  These  three  bodies  are  oxyphenol,  or  pyrocatechin,  resor- 
cin,  and  hydroquinone. 

Pyrocatechin. — This  body  is  so  named  because  it  was  first 
obtained  by  the  destructive  distillation  of  caoutchouc.  It  is 
also  produced  by  the  distillation  of  gum  kino  and  various  tan- 
nins which  produce  a  green  color  with  ferric  salts.  Pyroca- 
techin is  a  solid  body,  very  soluble  in  water  and  alcohol,  very 
slightly  soluble  in  ether ;  it  crystallizes  from  its  aqueous  solu- 
tion in  rectangular  prisms,  belonging  to  the  orthorhombic  sys- 
tem. It  melts  at  111.8°,  and  sublimes  below  that  temperature 
in  brilliant,  colorless  plates.  It  boils  between  240  and  245°. 
Its  odor  is  strong  and  excites  sneezing.  It  has  the  character 
of  an  acid,  like  phenol  itself.  It  dissolves  in  the  alkalies  and 
in  the  alkaline  carbonates.  When  exposed  to  the  air,  these 
solutions  become  colored,  first  green,  then  brown  and  black. 
An  aqueous  solution  of  pyrocatechin  produces  a  deep-green 
color  with  ferric  chloride,  which  changes  to  dark-red  on  the 
addition  of  an  alkali. 

Resorcin. — This  body,  which  is  the  homologue  of  orcin, 
C7H802,  is  formed  when  certain  gums,  such  as  galbanum, 
asafoetida,  gum  ammoniac,  sagapenum,  etc.,  are  fused  with 
potassium  hydrate  (Hlasiwetz  and  Earth).  It  is  extracted 
from  the  fused  mass  by  dissolving  the  latter  in  water,  super- 
saturating with  sulphuric  acid,  filtering,  and  agitating  the  fil- 
tered solution  with  ether,  which  dissolves  the  resorcin.  After 
having  driven  off  the  ether  on  a  water-bath,  a  residue  is  ob- 
tained which  is  distilled  :  the  resorcin  sublimes  and  condenses 
in  radiated  crystals. 

Oppenheim  and  Vogt  obtained  resorcin  by  fusing  chloro- 
phenylsulphurous  acid  with  potassium  hydrate.  The  former 
body  is  obtained  when  chlorobenzol  is  treated  with  sulphuric 
acid. 

C6H5C1        +         H'SO*     =      H2Q       + 

Chlorobenzol.  Chlorophenyl- 

sul jilinnius  acid. 

C6H4<c°3K   +  2KOH  =  KC1  +  K'SO3  +  WR*  j  ™ 

Potassium  clilomphenyl-  Resorcin. 

sulphite. 

Resorcin  forms  colorless,  prismatic  or  tabular  crystals.  It 
melts  at  110°,  and  boils  at  271°.  It  is  very  soluble  in  water, 
alcohol,  and  ether. 


616  ELEMENTS   OP   MODERN   CHEMISTRY. 


QUINONE   AND   HYDROQUINONE. 

Quinone,  C6H*02. — This  remarkable  body,  discovered  by 
Woskresensky,  is  a  product  of  the  oxidation  of  quinic  acid, 
which  exists  in  cinchona  bark.  It  may  be  obtained  by  dis- 
tilling that  acid  with  a  mixture  of  manganese  dioxide  and 
sulphuric  acid.  The  mass  swells  up  and  disengages  vapors  of 
quinone,  which  condense  in  the  receiver  in  brilliant,  golden- 
yellow  needles.  They  are  pressed  between  folds  of  filter-paper 
and  purified  by  resublimation. 

Quinone  crystallizes  in  long,  brilliant,  transparent  needles  of 
a  golden-yellow  color.  It  is  very  soluble  in  cold  water,  and 
more  soluble  in  alcohol  and  ether.  It  melts  at  115.7°  to  a 
yellow  liquid,  which  at  115.2°  solidifies  to  a  crystalline  mass. 
It  sublimes  at  ordinary  temperatures,  emitting  pungent  vapors 
which  excite  tears. 

Chlorine  converts  it  into  a  trichloro-derivative,  C6HCF02, 
crystallizable  in  small,  yellow  prisms,  fusible  at  164-166°. 

When  treated  with  a  mixture  of  potassium  chlorate  and 
hydrochloric  acid,  quinone  is  converted  into  tetrachloroquinone, 
C6C1402,  better  known  as  chloraline.  This  name  was  given  by 
Erdmann,  who  first  obtained  this  body  by  the  action  of  chlorine 
on  indigo,  of  which  the  Portuguese  name  is  anil.  The  same 
body  is  formed  by  the  action  of  a  mixture  of  potassium  chlorate 
and  hydrochloric  acid  on  a  great  number  of  aromatic  com- 
pounds, such  as  phenol,  picric  acid,  salicylic  acid,  salicin,  isatine, 
etc.  Tetrachloroquinone  forms  pale-yellow  scales,  having  a 
pearly,  metallic  lustre.  When  gently  heated,  it  sublimes  with- 
out fusing,  and  leaves  no  residue.  It  is  insoluble  in  water  and 
almost  insoluble  in  cold  alcohol,  but  dissolves  in  boiling  alcohol 
and  separates  on  cooling  in  golden-yellow  scales. 

Hydroquinone,  C6H602. — This  body  is  formed  by  the  action 
of  reducing  agents,  such  as  nascent  hydrogen,  hydriodic  acid, 
or  sulphurous  acid,  on  quinone. 

C6H*02  +  H2  =  C6H60' 

Wohler,  who  discovered  it,  found  it  also  among  the  products 
of  the  dry  distillation  of  quinic  acid. 

Hydroquinone  crystallizes  in  beautiful,  transparent,  and  col- 
orless, right  rhombic  prisms.  It  has  no  odor  ;  its  taste  is 
sweetish.  It  dissolves  in  17  parts  of  water  at  15°,  and  is  very 


QUINONE   AND   HYDROQUINONE.  617 

soluble  in  alcohol  and  ether.  It  melts  at  177.5°,  and  solidifies 
at  165°.  When  gently  heated,  it  sublimes  in  brilliant  plates, 
like  those  of  sublimed  benzoic  acid.  It  partially  decomposes 
when  abruptly  heated.  When  its  vapor  is  passed  through  a 
tube  heated  to  dull  redness,  it  breaks  up  into  quinone  and 
hydrogen.  Various  oxidizing  agents,  such  as  chlorine,  ferric 
chloride,  nitric  acid,  silver  nitrate,  and  potassium  dichromate, 
transform  it  into  a  substance  which  deposits  in  magnificent 
green  needles,  having  a  metallic  reflection.  It  is  quinhydrone 
or  green  hydroquinone,  C12H1004,  a  combination  of  quinone  and 
hydroquinone. 

Constitution  of  Quinone  and  Hydroquinone.  —  According 
to  Graebe,  these  bodies  are  allied  to  benzol,  from  which  the  first 
is  derived  by  the  substitution  of  two  atoms  of  oxygen  for  two 
atoms  of  hydrogen  ;  but  as  the  two  atoms  of  oxygen  represent 
four  atomicities,  of  which  two  only  are  employed  in  replacing 
H2  in  benzol,  the  other  two  serve  to  bind  together  the  two 
atoms  of  oxygen.  The  couple  (0"-0")"  can  indeed  play  the 
part  of  a  diatomic  group.  In  the  formation  of  hydroquinone, 
these  atoms  of  oxygen  separate  from  each  other  and  each  fixes 
one  atom  of  hydrogen,  so  that  two  hydroxyl  groups  are  formed 
and  substituted  each  for  one  atom  of  hydrogen  in  benzol.  The 
following  formulae  express  these  relations  : 


Benzol.  Quinone.  Hydroquinone. 

This  view  is  generally  adopted,  but  it  is  not  established  with 
certainty.  It  may  be  that  each  atom  of  oxygen  is  united  by 
both  of  its  atomicities  to  a  carbon  atom.  In  this  case  it  would 
be  necessary  to  admit  that  the  constitution  of  the  benzol  nucleus 
is  modified,  in  that  the  double  bond  uniting  two  carbon  atoms 
would  be  resolved  into  one. 

H  H  H 


HC      CH                          HC      C-0  HC      C=0  m 

i       it                                 i       H    i  or              ii       (?) 

HC      CH                          HC      C-0  HC      C=0 

V                    V  V 

H                                      H  H 

Benzol.                                 Quinone.  Quinone. 

Bodies  anologous  to  quinone  and  hydroquinone  have  been 
obtained  from  naphthalene  and  anthracene. 

52* 


618  ELEMENTS   OF   MODERN   CHEMISTRY. 


PHLOROGLUCIN. 

C6HK)3=C6H3(OH)3 

Phloroglucin  and  its  isomeride  pyrogallol  are  trioxyphenols, 
and  represent  benzol  in  which  three  atoms  of  hydrogen  are 
replaced  by  three  hydroxyl  groups.  The  relations  between 
phloroglucin,  oxyphenol,  and  phenol,  are  the  same  as  those 
between  glycerin,  propylglycol,  and  propyl  alcohol. 

fOTT  COH 

COT.OH  C3H6    Xw  OWWOH 

1  OH  1  OH 

Propyl  alcohol.  Propylglycol.  Glycerin. 

OH 


( 
PHM 


Phenol.  Oxyphenol.  Phloroglucin. 

Phloroglucin  was  discovered  by  Hlasiwetz,  who  obtained  it 
by  heating  phloretin  (page  589)  with  a  very  concentrated  solu- 
tion of  potassa.  It  is  also  formed  in  many  other  reactions, 
especially  when  gum-kino,  gamboge,  and  dragon's-blood  are 
fused  with  potassium  hydrate. 

Phloroglucin  crystallizes  in  hard,  rhombic  prisms,  having  a 
very  sweet  taste.  It  is  quite  soluble  in  water,  alcohol,  and 
ether.  Its  aqueous  solution  is  neutral.  Its  ethereal  solution, 
evaporated  upon  a  microscope  slide,  deposits  prisms  in  tangled, 
tree-like  forms  which  are  very  characteristic. 

The  crystals  deposited  from  ether  are  anhydrous,  while  those 
formed  in  water  contain  two  molecules  of  water  of  crystalliza- 
tion, which  they  lose  at  100°.  The  dry  crystals  melt  at  220°. 

TOLUOL  AND  ITS  DERIVATIVES. 

Toluol  is  a  homologue  of  benzol.  It  was  discovered  in  1837 
by  Pelletier  and  Walter ;  H.  Deville  has  obtained  it  by  distil- 
ling balsam  of  Tolu ;  hence  its  name.  It  exists  in  coal-tar, 
and  may  be  separated  from  that  body,  like  benzol,  by  fractional 
distillation.  Its  density  at  0°  is  0.882.  It  boils  at  111°.  It 
is  methyl-phenyl,  or  methyl-benzol,  and  has  been  obtained  by 
synthesis  by  heating  a  mixture  of  methyl  iodide  and  monobro- 
mobenzol  with  sodium  (Fit-tig  and  Tollens). 

C6H5Br     -f  CH3I  +  2Na  =  Nal  +  NaBr  -f-  C6H5-CH3 

Monobromobenzol.  Methyl-phenyl. 


TOLUOL.  619 

A  method  of  synthesis  of  toluol,  which  by  the  generality  of 
its  applications  is  one  of  the  most  fecund  in  chemistry,  is  due 
to  Friedel  and  Crafts.  It  consists  in  the  reaction  of  methyl 
chloride  on  benzol  in  presence  of  aluminium  chloride.  Toluol  is 
formed,  and  hydrochloric  acid  is  disengaged.  It  is  probable  that 
the  aluminium  chloride  first  acts  on  the  benzol,  disengaging 
hydrochloric  acid  and  forming  a  phenyl  derivative  of  aluminium 
chloride,  which  derivative  is  continually  formed  and  continually 
decomposed  by  the  methyl  chloride.  The  cycle  of  reactions 
would  then  be  represented  by  the  following  two  equations : 

C6H6  -f  APC16  =  APC15(C6H5)  -f  HC1 
APC15(C6H5)  +  CH3C1  =  C6H5(CH3)  +  APC16 

We  may  add  that  the  toluol  thus  formed  may  react  with  an 
excess  of  methyl  chloride,  forming  hydrochloric  acid  and  dime- 
thyl benzol  (xylol),  which  in  its  turn  may  react  upon  an  excess 
of  methyl  chloride.  It  is  thus  seen  that  the  methylation  of 
benzol  does  not  stop  with  the  first  substitution  compound,  and 
that  the  nature  of  the  products  formed  depends  upon  the  pro- 
portions of  the  bodies  which  react.  Friedel  and  Crafts  have 
thus  succeeded  in  introducing  six  methyl  groups  into  benzol, 
and  have  made  the  synthesis  of  hexamethylbenzol. 
C6H6  +  6CH3C1  =  6HC1  +  C<\  CH3)6 

Hexamethylbenzol. 

When  toluol  is  boiled  with  dilute  nitric  acid,  or  with  a  solu- 
tion of  chromic  acid,  it  is  transformed  into  benzoic  acid. 

Substitution  Products  of  Toluol. — These  compounds  are 
numerous,  and  present  various  isomerisms,  of  which  we  will 
consider  the  principles. 

C6H5 

When  chlorine  acts  upon  toluol,  I        ,  one  or  more  atoms 

CH. 

of  hydrogen  may  be  removed  and  replaced  by  as  many  atoms 
of  chlorine.  The  most  simple  of  the  products  thus  formed  is 
the  compound  C7H7C1,  which  results  from  the  substitution  of 
one  atom  of  chlorine  for  one  atom  of  hydrogen  in  toluol,  C7H8. 
But  this  substitution  may  take  place  in  the  benzol  nucleus 
C6!!5,  or  in  the  lateral  chain  CH3,  and  two  isomeric  bodies  are 
thus  formed,  monochlorotoluol  and  benzyl  chloride. 

C6H*C1  CW 

CH3  CH2C1 

Monochlorotoluols.  Benzyl  chloride. 


620  ELEMENTS   OF    MODERN   CHEMISTRY. 

PIT3 
Monochlorotoluol,  OW-O-w    ,  is  a  di-substituted  derivative 


of  benzol  ;  it  may  consequently  exist  in  three  isomeric  modifi- 
cations, as  has  already  been  explained  (page  594). 

It  is  thus  seen  that  there  are  four  different  bodies  derived 
from  toluol  by  the  substitution  of  one  atom  of  chlorine  for  one 
of  hydrogen,  namely,  benzyl  chloride  and  three  inonochloro- 
toluols. 

The  followin    table  includes  a  number  of  toluol  derivatives  : 


C6H4(NH2)     C«H4(OH)  C«H*(OH) 

CH3  CH3  CH3                                    CHO              CO.OH 

Monochlo-  Toluidine.  Cresol.                                       Salicyl       Salicylic  acid. 
rotolnol.                                                                                      hydride. 

C«H8  C6H*  C6H5  C6R5           C6H5 

CH2C1       CH2(NH2)      CIROH          CHO  CO.OH 

Benzyl  Benzyla-  Benzyl  Benzyl        Benzole  acid. 

chloride.  mine.  alcotiol.         aldehyde. 

Among  these  compounds,  those  placed  in  the  same  vertical 
line  present  isomerisrns  easily  understood  from  the  formulae, 
which  express  their  constitutions  and  show  the  atomic  group- 
ings. 

Those  bodies  in  the  first  horizontal  series  constitute  di-sub- 
stituted compounds  of  benzol. 


Toluidines.  Cresola.  Salicyl  hydride.  Salicylic  acid. 

Hence  they  may  exist  in  three  different  isomeric  modifica- 
tions, and  consequently  there  are  four  isomerides  of  each  of 
these  derivatives  of  toluol,  excepting  salicylic  acid,  just  as  for 
monochlorotoluol. 

Chloro-Derivatives  of  Toluol.—  Benzyl  chloride,  C6H5- 
CH2C1,  is  formed  when  chlorine  is  passed  into  boiling  toluol. 
It  is  a  colorless  liquid,  having  an  irritating  odor,  and  boiling 
at  1*76°. 

The  monochlorotoluols  are  formed  by  the  action  of  chlorine 
on  cold  toluol.  Ortho-  and  metachlorotoluol  are  liquids,  boil- 
ing between  156  and  157°  Parachlorotoluol  boils  at  160.5°, 
and  below  0°  solidifies  to  a  mass  which  melts  at  6.5°. 

Nitrotoluols.  —  Monohydrated  nitric  acid  attacks  toluol  and 
converts  it  into  nitrotoluol,  C7H7(N02),  and  dinitrotoluols, 

according  to  the  duration  of  the  reaction.     There  are  three 

pus 
nitrotoluols, 


CRESOLS  —  ORCIN.  621 

Orthonitrotoluol,  a  yellow  liquid,  boiling  between  222  and 
223°. 

Metanitrotoluol,  crystals,  fusible  at  16°.     Boils  at  230-231  °. 

Paranitrotoluol,  almost  colorless  prisms,  fusible  at  54°,  and 
boiling  at  236°. 

Dinitrotoluol,  C6H3(N02)2CH3,  is  formed  when  toluol  is 
treated  with  a  mixture  of  nitric  and  sulphuric  acids.  Long 
needles,  almost  colorless,  fusible  at  70.5°.  An  isomeride  is 
known,  fusible  at  60°. 

CRESOLS. 


There  are  three  cresols,  two  solid  and  one  liquid.  They 
may  be  formed  artificially  by  treating  toluol  with  sulphuric  acid, 
according  to  the  process  indicated  on  page  606  ;  but  in  this 
reaction  several  isomeric  sulphoconjugated  acids  are  formed, 
and  when  decomposed  by  potassium  hydrate,  they  yield  differ- 
ent cresols. 

The  liquid  cresol  discovered  by  Fairlie,  and  extracted  from 
wood-tar  by  Duclos,  is  a  colorless  liquid,  having  an  odor  like 
that  of  phenol.  It  boils  at  189-190°.  It  appears  to  be  a 
mixture. 

Orthocresol  is  a  crystalline  mass,  fusible  at  31°,  and  boiling 
at  185-186°. 

Metacresol  is  liquid. 

Paracresol  forms  colorless  prisms,  fusible  at  34.5°.  It  boils 
at  201°  (A.  Wurtz). 

ORCIN. 


This  body  is  an  oxycresol.  It  was  discovered  by  Robiquet 
in  1829,  and  is  obtained,  at  the  same  time  as  erythrite,  by 
decomposing  erythrin  by  slaked  lime  at  150°. 

The  orcin  is  deposited  first  in  beautiful  crystals  from  the 
solution  which  contains  both  substances,  and  it  is  purified  by 
recrystallization.  It  forms  colorless,  hexagonal  prisms,  con- 
taining one  molecule  of  water  of  crystallization.  It  melts  at 
58°,  losing  its  water,  and  the  anhydrous  orcin  boils  at  290°. 

The  crystals  of  orcin  become  rose-colored  in  the  air.  When 
ammonia  is  added  to  their  aqueous  solution  and  the  liquid  is 


622  ELEMENTS   OF   MODERN   CHEMISTRY. 

exposed  to  the  air,  it  absorbs  oxygen  and  assumes  first  a  violet 
color  and  afterwards  a  brown.  A  nitrogenized  body  is  formed 
which  is  known  as  orcein,  and  constitutes  the  coloring  principle 
of  the  orchil  of  commerce. 

The  synthesis  of  orcin  has  been  made  by  the  action  of  fused 
potassium  hydrate  on  the  sulphoconjugated  acid  of  mono- 
chlorotoluol  (cresyl  chloride,  C6H4C1.CH3).  The  chlorine  and 
the  group,  SO3H,  of  this  compound  are  thus  replaced  by  two 
groups  OH  (Vogt  and  Henninger). 

fCl  (OH 

C«H3  \  S03K     4-  2KOH     =    S03K*    +     KC1    +     C^H3  4  OH 
(  CH3  [  CH» 

Potassium  chlorocresyl-  Orcin. 

sulphite. 

TOLUIDINES. 

C7H9X  =  C6H4(NH2)-CH» 

Paratoluidine.  —  Solid  toluidine,  which  is  paratoluidine,  was 
discovered  by  Hofinann  and  Muspratt  in  1848.  They  obtained 
it  by  the  reduction  of  paranitrotoluol  by  ammonium  sulphy- 
drate.  This  reduction  may  also  be  accomplished  by  iron  and 
acetic  acid,  or  by  tin  and  hydrochloric  acid. 

C7H7(N02)     +     3H2    =    C7H7(NH2)     +     2H20 

Nitrotoluol.  Toluidine. 

An  interesting  method  of  formation  of  paratoluidine  was  dis- 
covered by  Hofmann  and  Martius.  When  methylaniline  hydro- 
chloride  is  heated  to  350°  under  pressure,  paratoluidine  hydro- 
chloride  is  formed.  The  methyl  group  which  is  united  to  the 
nitrogen  of  the  former  base  is  then  transposed  and  exchanged 
for  an  atom  of  hydrogen  of  the  phenyl  group. 


H  H 

Methylaniline.  Toluidine. 

Paratoluidine  is  a  solid  heavier  than  water.  It  crystallizes 
from  its  dilute  alcoholic  solution  in  large  plates.  It  melts  at 
45°,  and  boils  at  198°.  It  is  almost  insoluble  in  water,  but 
very  soluble  in  alcohol  and  in  ether. 

Toluidine  exists  nearly  always  in  commercial  aniline.  It  is 
important  and  necessary  for  the  preparation  of  certain  aniline 
colors. 

Orthotoluidine  was  discovered  by  Rosenstiehl  in  commercial 


BENZYL   ALCOHOL.  623 

toluidine,  which  is  a  mixture  of  para-  and  orthotoluidine.  It  is 
formed  by  the  reduction  of  orthonitrotoluol  by  nascent  hy- 
drogen. It  is  liquid  and  does  not  solidify  at  — 20°.  It  boils 
at  199.5°. 

Metatoluidine — A  colorless  liquid,  boiling  at  197°.  Density 
at  25°,  0.998. 

BENZYL  ALCOHOL. 
C7H8O  =  C«U5-CH2.OH 

Cannizzaro  obtained  this  body  by  heating  oil  of  bitter 
almonds  with  an  alcoholic  solution  of  potassium  hydrate. 

2C7H6O     +     KOH    =    KC7H502     +     C7H80 

Benzyl  aldehyde.  Potassium  benzoate.       Benzyl  alcohol. 

Toluol  may  be  converted  into  benzyl  alcohol.  It  is  boiled 
in  a  current  of  chlorine,  and  benzyl  chloride  is  thus  formed, 
C7H7C1.*  This  chloride  may  be  transformed  into  benzyl 
alcohol  by  heating  it  with  potassium  acetate  and  decomposing 
the  benzyl  acetate  so  formed  by  potassa. 

C?H7C1     +     KC2H302    =     C2H302.C7H7     +     KC1 

Benzyl  chloride.  Benzyl  acetate. 

C7H7.C2H302    +     KOH    =     KC2H302     +      C7H7.OH 

Benzyl  acetate.  Benzyl  alcohol. 

Benzyl  alcohol,  or  benzyl  hydrate,  is  a  colorless,  oily  liquid, 
having  a  faint  but  agreeable  odor.  It  boils  at  20*7°.  Density 
at  0°,  1.0628. 

When  heated  with  nitric  acid,  it  is  converted  into  benzyl 
aldehyde  (oil  of  bitter  almonds). 

C7H80  +  0  =  H20  +  C7H«0 
Chromic  acid  oxidizes  it  to  benzoic  acid. 

C7H80  +  O2  =  H20  +  C7H602 

The  relations  between  benzyl  alcohol,  benzyl  aldehyde,  and 
benzoic  acid  are  the  same  as  those  between  alcohol,  aldehyde, 
and  acetic  acid. 

CHS-CIF.OH  alcohol.  C6H5-CIROH  benzyl  alcohol. 

CHM3HO       aldehyde.  C*HM2HO        benzyl  aldehyde. 

CH3-C02H      acetic  acid.          C6H5-C02H       benzoic  acid. 

*  When  chlorine  is  passed  into  cold  toluol,  benzyl  chloride  is  not  formed, 
but  monochlorotoluol  (page  620). 


624  ELEMENTS   OF   MODERN   CHEMISTRY. 

Benzyl  Compounds. — Benzyl  chloride,  C7H7C1  =  C6H5- 
CH2C1,  is  formed,  as  has  already  been  remarked,  when  chlorine 
is  passed  into  boiling  toluol.  It  is  also  formed  by  the  action 
of  hydrochloric  acid  on  benzyl  alcohol  by  the  aid  of  heat.  It 
is  a  colorless  liquid  having  an  irritating  odor.  It  boils  at 
176°. 

Benzylamine,  C6H5-CH2.NH2.— This  body  is  formed  by  the 
action  of  nascent  hydrogen  on  benzonitrile  (phenyl  cyanide), 
which  thus  fixes  four  atoms  of  hydrogen.  It  is  also  formed 
in  small  quantity,  together  with  dibenzylamine  and  tribenzyl- 
amine,  when  benzyl  chloride  is  heated  with  alcoholic  ammonia. 
It  is  a  limpid  liquid,  boiling  at  185°,  and  miscible  with  water, 
alcohol,  and  ether.  Density,  0.99  at  14°. 

Trilenzylainine,  (C6H5.CH2)3N.— This  is  formed  in  abun- 
dance by  the  action  of  a  hot  alcoholic  solution  of  ammonia  on 
benzyl  chloride.  It  crystallizes  in  beautiful,  colorless  needles 
or  plates,  fusible  at  91°.  It  is  insoluble  in  water,  slightly 
soluble  in  cold  alcohol,  very  soluble  in  hot  alcohol  and  in  ether. 


BENZYL  ALDEHYDE. 

=  C6H5-CHO 


This  body,  also  called  benzoyl  hydride,  exists  in  the  essential 
oil  of  bitter  almonds,  mixed  with  hydrocyanic  acid,  both  sub- 
stances being  formed  by  the  action  of  emulsin  and  water  on 
amygdalin  (page  587). 

Benzyl  aldehyde  is  a  colorless,  strongly-refracting  liquid,  hav- 
ing a  pleasant  odor  and  a  pungent,  aromatic  taste.  It  boils  at 
179.5°. 

When  its  vapor  is  passed  through  a  porcelain  tube  filled  with 
pumice-stone  and  heated  to  redness,  benzyl  aldehyde  breaks  up 
into  benzol  and  carbon  monoxide. 

C7H60  =  CO  +  C6H6 

When  exposed  to  air  and  light,  it  absorbs  oxygen,  and  is  con- 
verted into  benzoic  acid. 

C7H60  +  O  =  C7H602 

Benzole  acid. 

Nascent  hydrogen,  produced  by  the   action  of   water  on 


BENZOYL   CHLORIDE.  625 

sodium  amalgam,  transforms  benzyl  aldehyde  into  benzyl  alco- 
hol (Friedel). 

C7H60  +  H2  =  C7H7.OH. 

Chlorine  and  bromine  convert  it  into  chloride  and  bromide 
of  benzoyl ;  hence  the  name  benzoyl  hydride. 

C7H5O.H     +     CP    =    HC1     +     C7H5O.C1 

Benzyl  aldehyde.  Benzoyl  chloride. 

When  crude  oil  of  bitter  almonds  containing  hydrocyanic 
acid  is  mixed  with  alcoholic  potassium  hydrate,  or  when  the 
pure  oil  is  mixed  with  an  alcoholic  solution  of  potassium  cya- 
nide, the  benzyl  aldehyde  is  polymerized  and  converted  into  a 
solid  body,  which  is  benzoin,  CUH1202.  The  latter  body  crystal- 
lizes in  brilliant,  colorless  prisms,  fusible  at  133-134°.  It  is 
but  slightly  soluble  in  water  and  cold  alcohol,  very  soluble  in 
boiling  alcohol. 

Benzoyl  Chloride,  C6H5-COC1.— This  body  is  also  formed 
by  the  action  of  phosphorus  pentachloride  on  benzoic  acid  or  a 
dry  benzoate.  It  is  a  colorless,  highly-refractive  liquid,  having 
a  peculiar,  irritating  odor.  It  boils  at  190°.  Water  decom- 
poses it  into  benzoic  and  hydrochloric  acids. 

C7H5O.C1  +  H2O  =  C7H5O.OH  +  HC1 
Ammonia  converts  it  into  benzamide. 

C7H5.OC1  +  Nil3  =  C7H5O.NH2  +  HC1 

Benzamide. 

Benzoyl  chloride  may  exchange  its  chlorine  for  other  ele- 
ments. When  it  is  distilled  with  potassium  iodide,  potassium 
chloride  and  benzoyl  iodide  are  formed.  Liebig  and  Wohler, 
who  discovered  these  important  reactions,  prepared  in  the 
same  manner,  by  double  decomposition,  benzoyl  sulphide  and 
benzoyl  cyanide.  These  experiments  are  celebrated ;  they 
were  the  starting-point  of  the  Lenzoyl  theory,  which  marked 
an  important  progress  in  the  development  of  the  theory  of 
radicals.  The  following  formulae  indicate  the  principal  benzoyl 
combinations : 

C7H*O.H  benzoyl  hydride  (oil  of  bitter  almonds). 

C7H5O.C1  benzoyl  chloride. 

C7H50.I  benzoyl  iodide. 

(C*H&0)a3  benzoyl  sulphide. 

C7H5O.OH  benzoyl  hydrate  (benzoic  acid). 

C*H5O.NH2  benzamide. 
2B  53 


626 


ELEMENTS    OF    MODERN    CHEMISTRY. 


BENZOIC    ACID. 

C7H6()2  =  OH5-CO2H 

Preparation. — This  acid  may  be  obtained  from  gum  benzoin. 
That  resin  is  placed  in  a  flat  dish  over  the  top  of  which  a  sheet 
of  tissue-paper,  or  light  filter-paper  is  glued  (Fig.  131).  This 
diaphragm  forms  the  base  of  a  paper  cone  which  is  then  placed 
over  the  dish,  which  is  moderately  heated  on  a  sand-bath  for 

several  hours.  At  the 
end  of  that  time,  the 
whole  is  allowed  to 
cool,  and  the  ben  zoic 
acid  is  found  in  light, 
brilliant,  crystalline 
flakes  on  the  sides  of 
the  cone,  and  on  the 
diaphragm. 

The  benzoin  resin 
may  also  be  powdered 
and  digested  with  milk 
of  lime  for  twenty- 
four  hours  ;  it  is  then 
heated  to  ebullition 
and  filtered.  Hydro- 
chloric acid  precipi- 
tates benzoic  acid  from  the  filtered  liquid,  which  contains  cal- 
cium benzoate. 

In  Germany,  large  quantities  of  benzoic  acid  are  prepared 
by  boiling  the  urine  of  horses  and  cows  with  hydrochloric  acid. 
The  hippuric  acid  which  these  urines  contain  is  thus  decom- 
posed into  benzoic  acid  and  glycocol.  The  benzoic  acid  crys- 
tallizes on  cooling,  and  is  purified  by  sublimation. 

Properties. — Benzoic  acid  crystallizes  in  needles,  or  in  thin, 
brilliant  plates.  It  has  an  aromatic  odor,  and  a  slightly  acid 
taste.  It  melts  at  121°,  and  boils  at  250°. 

It  dissolves  in  607  parts  of  water  at  0°,  and  in  about  12 
parts  of  boiling  water.  When  boiled  with  a  quantity  of  water 
insufficient  to  dissolve  it,  it  melts.  It  volatilizes  with  the  vapor 
of  water.  It  dissolves  readily  in  alcohol  and  in  ether.  When  its 
vapor  is  passed  over  red-hot  pumice-stone,  contained  in  a  porce- 
lain tube,  it  is  decomposed  into  carbonic  anhydride  and  benzol. 


FIG.  131. 


HIPPURIC   ACID.  627 

C7H602    =    CO2    +     C6H6 

When  heated  with  phosphorus  pentachloride,  it  yields  ben- 
zoyl  chloride. 

C7H5O.OH  +  POP  =  POCP  +  HC1  +  CTH5O.C1 

Benzamide,  C6H5-CO.NH2.—  This  body  is  formed  by  the 
action  of  ammonia  gas  on  benzoyl  chloride. 

C6H5CO.C1  +  2NH3  =  NH4C1  +  C6H5-CO.NH2 
It  is  also  formed  by  the  action  of  ammonia  on  ethyl  benzoate. 
C6H5-CO.OC*H5  +  NH3  =  C2H5.OH  +  C6H5-CO.NH2 

Etliyl  beuzoate.  Alcohol.  Benzamide. 

It  occurs  in  brilliant,  colorless,  oblique  rhombic  crystals, 
fusible  at  128°,  and  can  be  sublimed  without  decomposition. 
It  is  soluble  in  hot  water  and  in  alcohol. 

Benzole  Acetone,  Benzophenone,  or  Diphenyl-ketone, 
C13H10O  ==  C6H5-CO-C6H5.—  This  body  is  formed,  together 
with  benzol,  in  the  destructive  distillation  of  calcium  benzoate 
(Chancel). 

Ca(C6H5-C02)2       =       CaCO3       +       (C6H5)2CO 

Calcium  benzoate.  Diphenyl-ketone. 

It  forms  large,  colorless,  or  slightly  yellow,  right  rhombic 
prisms,  fusible  at  48-49°,  and  boils  at  295°.  It  is  insoluble 
in  water,  but  very  soluble  in  alcohol. 

Friedel  and  Crafts  obtained  it  by  treating  benzol  with  chloro- 
carbonic  gas  in  presence  of  aluminium  chloride. 

2C6H6  +  COC12  =  2HC1  +  (C6H5)2CO 

HIPPURIC  ACID. 


CO.OH 

One  of  the  most  important  of  the  benzoic  derivatives  is  hip- 
puric  acid.  Its  relations  with  the  benzoic  series  are  manifested 
by  its  decomposition  by  hydrochloric  acid  into  benzoic  acid  and 
glycocol. 

C9H9N03     +.     H20     =     C2H5N02      +       C7H602 

Hippuric  acid.  Glycocol.  Benzoic  acid. 

Rouelle,  Fourcroy,  and  Vauquelin  discovered  this  acid  in 
the  urine  of  the  horse,  but  confounded  it  with  benzoic  acid. 


628  ELEMENTS   OF    MODERN   CHEMISTRY. 

Its  true  nature  was  recognized  by  Liebig  in  1830.  Dessaignes 
has  made  its  synthesis  by  the  reaction  of  benzoyl  chloride  on 
the  zinc  compound  of  glycocol. 

C2H5N02  +  C7H5O.C1  =  C2H4(C7H50)N02  +  HC1 

Glycocol.  Ben/oyl  chloride.  Hippuric  acid. 

Hippuric  acid  is  obtained  from  the  urine  of  horses  and  cows 
by  mixing  the  urine  with  2  or  3  times  its  volume  of  concen- 
trated hydrochloric  acid.  The  hippuric  acid  separates  in  col- 
ored crystals. 

When  properly  purified,  it  crystallizes  in  long,  colorless 
prisms,  but  slightly  soluble  in  cold  water,  very  soluble  in  boil- 
ing water  and  in  alcohol.  When  heated  in  a  retort,  it  decom- 
poses and  yields  a  sublimate  of  benzoic  acid.  At  the  same 
time  a  certain  quantity  of  an  oily  body  having  a  disagreeable 
odor  distils:  it  is  phenyl  cyanide,  or  benzoriitrile,  CN.C6H5. 


SALICYL   ALDEHYDE,   OR  SALICYL   HYDRIDE. 

C7H602  =  C6H*(OH).CHO 

This  compound,  which  is  isomeric  with  benzoic  acid,  exists 
naturally  in  the  essential  oil  of  the  meadow-sweet  (Spirsea  ul- 
maria].  Piria  obtained  it  by  oxidizing  salicin  by  potassium 
dichromate  and  sulphuric  acid  (page  588). 

It  is  a  colorless,  highly  refracting  liquid,  and  boils  at  196.5°. 
Its  density  at  13.5°  is  1.173.  Its  odor  is  pleasant  and  its 
taste  burning.  It  is  quite  soluble  in  water,  and  dissolves  in 
alcohol  and  ether  in  all  proportions.  It  has  an  acid  reaction. 
It  produces  a  violet  color  with  ferric  chloride.  Oxidizing 
agents  convert  it  into  salicylic  acid. 

C7H602  +  O  =  C7H603 

By  the  action  of  fused  potassium  hydrate,  it  is  likewise 
transformed  into  salicylic  acid,  with  disengagement  of  hydrogen. 

C7H602    -f     KOH    =    KC7H503     +     H2 

Salicyl  aldehyde.  Potassium  snlicylate. 

In  presence  of  sodium  amalgam  and  water,  it  fixes  H2  and 
is  converted  into  saligenin  (Reincke  and  Beilstein). 

C7H602     +     H2    =     C7H802 

Salicyl  aldehyde.  Saligenin. 


SALICYLIC   ACID.  629 

The  latter  body  is  also  formed,  according  to  Piria,  by  the 
decomposition  of  salicin  by  ferments  and  acids  (page  588).  It 
crystallizes  in  tables  having  a  pearly  lustre,  or  in  small,  brilliant 
needles. 

SALICYLIC   ACID. 

CTH6O3  =  C6H*(OH).CO2H 

Formation  and  Preparation.  —  This  body  was  discovered 
by  Piria,  who  obtained  it,  in  1839,  by  fusing  salicyl  aldehyde 
with  potassium  hydrate. 

_  KQH  _.  KC7H503       H2 


Oil  of  meadow-sweet  contains  it  naturally,  together  with 
salicyl  aldehyde.  The  essential  oil  of  Gaultheria  procumbens 
(winter-green)  is  methyl  salicylate  (Cahours),  that  is,  sali- 
cylic acid,  in  which  the  atom  of  basic  hydrogen  is  replaced  by 
methyl. 

Salicylic  acid  is  ordinarily  prepared  by  boiling  oil  of  winter- 
green  with  caustic  potassa  as  long  as  methyl  alcohol  is  dis- 
engaged. Potassium  salicylate  is  formed,  and  is  afterwards 
decomposed  by  an  excess  of  hydrochloric  acid.  The  salicylic 
acid  separates,  and  is  purified  by  recrystallization  from  boiling 
water. 

Kolbe  and  Lautemann  formed  salicylic  acid  by  synthesis  by 
passing  carbon  dioxide  into  phenol  in  which  sodium  was  dis- 
solved. Sodium  salicylate  is  thus  formed. 

(HP.OH    +     CO.O    ==    C6H*(°H) 

CO.OH 

Phenol.  Salicylic  acid. 

Kolbe  has  recently  improved  this  process.  Indeed,  salicylic 
acid  is  formed  by  simply  passing  dry  carbon  dioxide  over 
sodium  phenate  at  a  temperature  of  180°.  The  temperature 
is  finally  raised  to  250°,  and  the  product  of  the  reaction,  freed 
from  an  excess  of  phenol  by  distillation,  constitutes  sodiuin- 
salicylate  of  sodium. 

2C6H5.ONa  +  CO2  ==  C6H5.OH  -f   C6H4  j  £^a 

Sodium  phenate.  Phenol.          Sodium-salicylate  of  sodium. 

The  mass  is  exhausted  with  water,  and  the  solution  is  treated 
with  hydrochloric  acid,  which  sets  free  the  salicylic  acid. 

53* 


630  ELEMENTS   OF   MODERN   CHEMISTRY. 

This  process  permits  of  the  rapid  and  economical  manu- 
facture of  large  quantities  of  salicylic  acid. 

Properties. — Salicylic  acid  crystallizes  from  its  alcoholic 
solution  in  large,  quadrilateral  prisms,  and  from  its  aqueous 
solution  in  long  needles.  It  melts  at  156°.  When  mixed  with 
pumice-stone  and  rapidly  distilled,  it  breaks  up  into  carbon 
dioxide  and  phenol. 

C7H603  =  CO2  +  C6H60 

It  is  very  soluble  in  alcohol  and  ether,  and  in  boiling  water, 
but  cold  water  scarcely  dissolves  it.  Its  aqueous  solution  pro- 
duces a  deep  violet  color  with  the  ferric  salts. 

When  salicylic  acid  is  treated  with  nitric  acid,  it  is  converted 
into  two  isomeric  nitrogenized  acids ;  both  are  nitrosalicylic 
adds,  C7H5(N02)03. 

a-nitrosalicylic  acid  crystallizes  in  long,  colorless  needles, 
which  are  anhydrous  and  melt  at  228°  ;  they  are  very  slightly 
soluble  in  cold  water.  It  produces  a  blood-red  color  with  ferric 
chloride. 

/5-nitrosalicylic  acid  crystallizes  in  long,  colorless  needles, 
containing  one  molecule  of  water  of  crystallization.  When 
heated,  it  loses  this  water  and  melts  at  144-145°.  It  is  slightly 
soluble  in  cold  water.  Its  solution  also  produces  a  blood-red 
color  with  ferric  chloride.  This  acid  is  also  formed  when 
indigo  is  long  boiled  with  nitric  acid.  It  was  formerly  called 
indigotic  acid. 

Salicylic  acid  possesses  antiseptic  properties  like  phenol, 
without  presenting  the  same  inconveniences  as  the  latter  as 
regards  odor  and  causticity. 

Methyl  Salicylate,  C7H5(CH3)03.— Cahours  first  recognized 
the  oil  of  Gaultheria,  known  as  essence  of  winter-green,  to  be 
methyl  salicylate.  When  purified,  this  body  forms  a  colorless 
oil,  having  a  pleasant  odor.  It  boils  at  223.7°.  Its  density  at 
0°  is  1.1969.  Like  the  phenols,  it  has  the  characters  of  a 
weak  acid.  When  a  concentrated  solution  of  potassium  hy- 
drate is  added  to  methyl  salicylate,  a  precipitate  of  potassium 
gaultherate  is  formed.  Cahours  discovered  the  existence  of  an 
isomeride  of  methyl  salicylate.  It  is  methylsalicylic  acid.  The 
following  formulae  indicate  the  constitutions  of  these  bodies  : 

C6H*.OH         C6H*.OH        C6H*.OK        C6H*.OCH3        CW.OCH3 

CO.OH  CO.OCH3        CO.OCH3        CO.OH  CO.OCII3 

Salicylic  acid.          Methyl  Potassium       Methytailicylic  Methyl 

salicylate.        gaultherate  acid.  methylsalicylate. 


OXYBENZOIC   AND   PAROXYBENZOIC   ACIDS.  631 


OXYBENZOIC   AND   PAROXYBENZOIC    ACIDS. 

These  two  acids  are  isomeric  with  salicylic  acid. 

Oxybenzoic  Acid  is  formed  under  various  circumstances  ; 
especially  when  metachloro-benzoic  acid,  a  chloro-derivative 
of  benzoic  acid,  is  heated  with  potassium  hydrate. 

C7H5C102  +  2KOH  =  C7H5(OK)02  +  KC1  -f  H20 

It  is  an  anhydrous,  crystalline  powder,  consisting  of  small, 
square  tables.  Sometimes  it  is  in  mammillated  crystals.  It  melts 
at  200°,  and  can  be  distilled  without  alteration.  It  is  only 
slightly  soluble  in  cold  water,  but  dissolves  more  readily  in  boil- 
ing water. 

Paroxybenzoic  Acid  is  formed  under  rather  remarkable  cir- 
cumstances. We  have  already  seen  that  in  presence  of  sodium, 
phenol  fixes  carbon  dioxide,  forming  sodium  salicylate.  If  the  so- 
dium be  replaced  by  potassium,  the  same  reaction  produces  potas- 
sium paroxybenzoate.  The  same  salt  is  formed  when  potassium 
phenate  is  heated  to  210  or  220°  in  a  current  of  carbon  dioxide. 

Paroxybenzoic  acid  crystallizes  in  transparent,  oblique  rhom- 
bic prisms,  containing  one  molecule  of  water  of  crystallization. 
When  anhydrous,  it  melts  at  110°.  It  is  much  more  soluble 
in  water  and  alcohol  than  salicylic  acid.  Its  aqueous  solution 
does  not  produce  a  violet  color  with  ferric  chloride. 

Anisic  Compounds.  —  When  the  oils  of  anise,  of  fennel,  or 
of  tarragon  are  heated  with  nitric  acid,  they  are  converted  into 
a  colorless  oil,  having  a  spicy  odor,  and  boiling  at  248°.  This 
is  anisic  aldehyde,  C8!!8^)2.  By  a  more  complete  oxidation, 
this  aldehyde  is  converted  in  anisic  acid,  C8H80\  Anisic  alde- 
hyde and  acid  present  very  simple  relations  of  composition  with 
paroxybenzoic  acid. 

Anisic  aldehyde  is  methylparoxybenzoic  aldehyde,  and  anisic 
acid  is  methylparoxybenzoic  acid. 


r«m^- 

<CO.OH 

Paroxybenzoic  acid.  Methylparox.vbenzoic,         Methylparoxy  benzoic, 

or  anisic  acid.  or  anisic  aldehyde. 

TYROSINE. 


This  body  seems  to  be  related  to  the  preceding  compounds. 
It  may  be  regarded  as  amidopropionic  acid  in  which  one  atom 


632  ELEMENTS   OF   MODERN   CHEMISTRY. 

of  hydrogen  is  replaced  by  the  group  C6H*.OH  (paroxyphenyl) 
as  it  exists  in  paroxybenzoic  acid. 


C02H  C02H  C02H 

Propionic  acid.    Amidopropionic  acid.  Oxyphenyl-amidopropionic 

acid  (tyrosine). 

Tyrosine  is  the  product  of  the  decomposition  of  many  nitro- 
genized  matters  in  the  animal  economy.  It  may  be  prepared 
by  boiling  for  sixteen  hours  1  part  of  horn  shavings  with  2 
parts  of  sulphuric  acid  diluted  with  4  times  its  volume  of  water. 
The  liquid  is  then  neutralized  with  milk  of  lime,  filtered,  the 
filtrate  evaporated  to  half  its  volume,  acidified  with  sulphuric 
acid,  and  treated  with  an  excess  of  lead  carbonate. 

The  solution,  which  contains  the  tyrosine  as  lead  salt,  is  de- 
composed by  hydrogen  sulphide,  filtered,  and  evaporated.  The 
tyrosine  crystallizes  out,  and  may  be  purified  by  several  crystal- 
lizations. The  mother-liquors  contain  leucine. 

Tyrosine  crystallizes  in  long,  colorless  needles,  often  united 
in  tufts.  It  is  but  slightly  soluble  in  water  and  in  cold  alcohol, 
more  soluble  in  hot  alcohol,  and  insoluble  in  ether.  It  forms 
definite  compounds  with  both  acids  and  bases.  When  fused 
with  potassium  hydrate,  it  breaks  up  into  paroxybenzoic  and 
acetic  acids,  and  ammonia. 

Tyrosine  may  be  recognized  by  the  following  reaction. 
When  its  aqueous  solution  is  boiled  with  a  solution  of  mer- 
curic nitrate,  as  neutral  as  possible,  a  voluminous  yellow  precip- 
itate is  formed,  which  assumes  a  deep  copper-red  color  by 
boiling  with  nitric  acid  containing  a  small  quantity  of  nitrous 
acid. 

GALLIC  ACID. 

C7H6Q5  =  C«H2(OH)3  -  CO.OH 

This  acid  is  closely  related  to  salicylic  acid.  It  is  dioxysali- 
cylic  acid,  and  Lautemann  obtained  it  by  treating  di-iodosali- 
cylic  acid  with  alkalies. 

C7H4FO3    +     2KOH    =    2KI     +     C7H4(OH)2O» 

Di-iodosalicylic  acid.  Gallic  acid. 

We  have  already  seen  that  gallic  acid  is  a  product  of  the 
decomposition  of  tannic  acid.  It  is  prepared  by  exposing 
coarsely-powdered  and  moistened  nut-galls  to  the  air,  renewing 
the  water  as  it  evaporates.  At  the  end  of  two  or  three  months 


INDIGO.  633 

a  black  liquid  is  separated  from  the  mass  by  strong  pressure, 
and  the  solid  residue  is  exhausted  with  boiling  water.  Gallic 
acid  crystallizes  out  on  the  cooling  of  the  filtered  liquid.  It  is 
purified  by  several  crystallizations  in  boiling  water. 

Gallic  acid  forms  long,  silky  needles,  which  contain  one 
molecule  of  water  of  crystallization.  It  has  no  odor  ;  its  taste 
is  astringent  and  slightly  acid.  When  heated  to  100°,  it  loses 
carbon  dioxide  and  is  converted  into  a  body  which  sublimes 
in  brilliant  white  laminae.  This  is  pyrogallol,  or  pyrogallic 
acid,  and  is  employed  in  photography. 

C7H605    =    CO2     +     C6H3(OH)3 

Gallic  acid.  Pyrogallul. 

Gallic  acid  dissolves  in  100  parts  of  cold  water,  and  in  3 
parts  of  boiling  water.  It  is  very  soluble  in  alcohol,  less  soluble 
in  ether.  Its  solution  gradually  absorbs  oxygen  when  exposed 
to  the  air,  and  at  the  same  time  becomes  colored  and  disengages 
carbon  dioxide. 

If  a  recently  boiled  solution  of  gallic  acid  be  passed  up  into 
a  tube  filled  with  mercury  and  containing  no  air,  and  some 
recently  boiled  baryta-water  be  then  added,  a  white  precipitate 
is  formed  which  at  once  changes  to  blue,  if  a  few  bubbles  of 
oxygen  be  introduced.  The  change  of  color  is  the  indication 
of  an  oxidation  of  the  gallic  acid,  favored  in  this  case  by  the 
presence  of  the  alkali. 

INDIGO. 
C8H5NO 

Indigo  is  obtained  from  different  species  of  the  genus  Indi- 
gofera.  The  pastel,  or  woad  (Isatis  tinctoria),  also  furnishes  a 
coloring  matter  identical  with  indigo. 

In  India,  indigo  is  prepared  by  macerating  the  stems  and 
leaves  of  the  indigofera,  collected  at  the  time  of  flowering,  with 
water,  in  vats  where  they  are  allowed  to  ferment.  In  12  or 
15  hours  the  liquid  is  drawn  off  into  other  vats,  where  it  is 
agitated  so  as  to  bring  it  in  contact  with  the  air,  an  opera- 
tion which  occasions  the  formation  of  a  blue  precipitate.  The 
brown  liquor  is  then  drawn  off,  and  the  deposit  is  boiled  in 
copper  vessels ;  it  is  then  pressed  between  cloths  and  cut  into 
cubical  pieces  and  dried.  In  this  form  the  indigo  is  delivered 
to  commerce. 

Indigo  is  not  contained  ready  formed  in  the  plants  which 

2B* 


634  ELEMENTS   OF   MODERN   CHEMISTRY. 

serve  for  its  manufacture.    Schunck  has  shown  that  these  plants 
contain  a  substance  analogous  to  the  glucosides,  indican,  which 
is  decomposed  by  fermentation  into  indigo  and  indogludn. 
C26H3iN0.7  +  2H20  ==  C8H5NO  +  3C6H1006 

Indican.  Indigo.  Indoglucin. 

Indican  has  been  found  in  human  urine. 

The  indigo  of  commerce  contains  from  50  to  90  per  cent,  of 
coloring  matter.  It  generally  occurs  in  irregular  masses,  some- 
times cubical,  of  which  the  shade  varies  from  violet-blue  to 
blackish-blue.  The  most  esteemed  varieties  present  a  brilliant 
coppery  reflection. 

Pure  indigo  is  called  indigotine.  It  may  be  obtained  by 
heating  the  indigo  of  commerce  in  a  current  of  hydrogen,  or 
by  subliming  it  in  small  quantities  between  two  watch-glasses 
(Chevreul).  It  then  forms  right  rhombic  prisms  having  four 
or  six  faces.  Indigotine  is  insoluble  in  water,  in  cold  alcohol, 
and  in  ether.  Boiling  alcohol  and  oil  of  turpentine  dissolve  it 
to  a  slight  extent. 

Concentrated,  or  better,  fuming  sulphuric  acid  dissolves  in- 
digo at  50  or  60°,  forming  a  beautiful  blue  solution,  which 
contains  two  acids,  sulphmdigotic  acid,  C8H*NO.S03H,  and 
sulphopurpuric  acid,  C16H9N202.S03H.  The  solution  of  indigo 
in  sulphuric  acid  is  used  in  dyeing ;  it  is  prepared  by  dissolving 
indigo  in  a  hot  mixture  of  fuming  and  ordinary  sulphuric  acids. 
The  blue  solution  thus  obtained  is  known  as  sulphate  of  indigo, 
Saxon  blue,  or  composition  blue. 

Boiling  dilute  nitric  acid  converts  indigo  into  isatin.  The 
concentrated  acid  converts  it  first  into  nitrosalicylic  acid,  C7H5 
(N02jO:{,  and  then  into  picric  acid. 

When  heated  with  potassium  hydrate,  indigo  is  converted 
into  anthranilic  acid,  C7H5(NH2)02,  or  into  salicylic  acid, 
which  is  formed  at  the  expense  of  the  anthranilic  acid. 

C7H5(NH2)02     +     KOH     =    KC7H503     +     NH3 

Anthranilic  acid.  Potassium  salicylate. 

When  indigo  is  distilled  with  potassium  hydrate,  aniline 
passes  over,  being  formed  at  the  expense  of  the  anthranilic  acid 
first  formed. 

C7H7N02     =     CO2     +     C6H7N 

Anthranilic  acid.  Aniline. 

White  Indigo,  C16H12N202.—  This  body,  which  was  discov- 
ered by  Chevreul  in  1812,  results  from  the  action  of  nascent 


ISATIN.  635 

hydrogen  on  indigo.     It  is  produced  when  the  latter  substance 
is  submitted  to  the  action  of  alkaline  solutions  in  presence  of 
reducing  matters,   such   as  sulphurous  or  phosphorous  acid, 
hydrogen  sulphide,  iron,  zinc,  or  ferrous  or  stannous  hydrate. 
2C8H5NO  -f  H2  =  C16H12N202 

White  indigo  is  ordinarily  prepared  by  introducing  a  mix- 
ture of  indigo,  ferrous  sulphate,  slaked  lime,  and  water  into  a 
vessel,  which  should  be  entirely  filled  with  the  mixture  and 
then  hermetically  sealed  and  allowed  to  stand  for  two  days.  A 
clear,  alkaline  solution  is  thus  obtained,  which  is  decanted,  and 
supersaturated  with  hydrochloric  acid,  out  of  contact  with  the 
air.  A  deposit  of  white  indigo  is  formed,  and  must  be  collected 
on  a  filter,  rapidly  washed  with  boiled  water,  and  dried  in  a 
vacuum. 

The  body  thus  obtained  has  a  dirty-white  color,  and  is  with- 
out either  taste  or  smell.  It  is  insoluble  in  water,  but  dissolves 
with  a  yellow  color  in  alcohol,  ether,  and  alkaline  solutions. 
On  contact  with  air  it  absorbs  oxygen,  and  is  converted  into 
blue  indigo.  Nitric  acid  rapidly  brings  about  this  transformation. 

Uses. — Indigo  is  largely  used  in  dyeing.  The  principle  of 
its  application  depends  on  the  conversion  of  the  blue  indigo  into 
white  indigo  by  reducing  agents.  The  reduced  white  indigo 
is  soluble  in  alkaline  solutions  and  in  this  form  is  fixed  on  the 
fabrics,  after  which  it  is  reconverted  into  blue  indigo  by  ex- 
posure to  the  air.  The  mixture  just  indicated  for  the  prepara- 
tion of  white  indigo  (ferrous  sulphate,  indigo,  lime,  and  water) 
is  most  frequently  employed.  It  constitutes  what  is  known  as 
the  vitriol  vat. 

Schiitzenberger  and  de  Lalande  have  recently  described  a 
process  of  dyeing  with  indigo,  based  on  the  employment  of 
sodium  hydrosulphite. 

ISATIN. 
C8H5NO2 

This  body  was  discovered  by  Erdmann  and  Laurent  in  1841. 
It  is  a  product  of  the  oxidation  of  indigo  by  dilute  nitric  acid. 
C4PNO  +  O  =  C8H5N02 

Pure  isatin  crystallizes  sometimes  in  large,  dark,  gold- 
colored  prisms,  sometimes  in  small,  reddish-yellow  prisms 
having  a  brilliant  lustre.  It  is  only  slightly  soluble  in  cold 
water  and  in  ether,  but  more  soluble  in  boiling  water,  and  very 


636  ELEMENTS   OF   MODERN    CHEMISTRY. 

soluble   in  alcohol.     When   distilled  with   potassa}  it   yields 
aniline. 
C8H5N02    -f    4KOH    =±    2K2C03    -f    C6H7N    +    H2 

Isatin.  Aniline. 

By  the  action  of  chlorine,  isatin  yields  substitution  pro- 
ducts. These  latter  break  up,  like  isatin  itself,  by  the  action 
of  potassium  hydrate,  yielding  chloranilines  (Hofinann). 

C8H4C1N02  -f-  4KOH  =  2K2C03  -f  C6H6C1N  -f  H1 

Monochlorisatiu.  Monochlora  inline. 

Products  of  the  Reduction  of  Isatin.  —  To  isatin  are  re- 
lated certain  products  of  its  reduction,  which  are  interesting 
and  which  have  been  studied  by  Knop  and  Baeyer.  They  are 

Dioxindol  C8IFN02 
Oxindol  C8R7NO 
Indol  C8H7N 

The  first  two  are  formed  successively  by  the  action  of  sodium 
amalgam  on  an  aqueous  solution  of  isatin. 

C8H5N02    +     H2    =     C8H7N02 

Isatin.  Dioxindol. 

C8H7N02     -f     H2    =     C8H7NO     -f     H20 

Dioxindol.  Oxindol. 

By  reducing  oxindol  by  zinc  powder  with  the  aid  of  heat, 
Baeyer  obtained  indol. 

C8H7NO     -f     Zn     =     C8H7N     -f-     ZnO 

Oxindol.  Indol. 

Indol  is  a  crystallizable  solid,  fusible  at  52°.  It  volatilizes 
with  the  vapor  of  water.  Its  odor  recalls  that  of  naphty- 
lamine.  It  dissolves  readily  in  boiling  water,  and  in  alcohol 
and  ether.  It  has  basic  properties. 

Baeyer  has  recently  obtained  isatin  and  indigo  by  synthesis. 
By  heating  phenyl-acetic  acid  with  nitric  acid,  and  reducing 
the  nitro-compound  so  formed,  oxindol  is  obtained. 


This  is  converted  into  nitroso-oxindol,  C'H^CO,  and 
this  by  reduction  yields  c«H*-<^^!b^CO.  By  oxidizing  the 
latter  compound,  isatin  is  obtained,  C«H*<£g>CO.  When  isa- 
tin is  heated  with  phosphorus  pentachloride,  hydrochloric  acid 
is  disengaged,  and  a  chloro-compound  is  formed, 

and  this  by  reduction  yields  indigo, 


PHTHALIC    ACID.  637 


XYLOLS   AND   DERIVATIVES. 


That  portion  of  coal-tar  which  boils  between  136  and  139° 
contains  a  mixture  of  isomeric  hydrocarbons,  which  is  desi^- 

CH3 

nated  as  xylol  or  xylene.     It  is  dimethylbenzol, 


and  can  exist  in  three  different  isomeric  modifications,  like  all 
of  the  di-substituted  derivatives  of  benzol. 

Metaxylol,  which  boils  at  137°,  predominates  in  the  mixture 
of  xylols  which  is  obtained  from  coal-tar.  When  oxidized  by 
chomic  acid,  it  is  converted  into  isophthalic  acid,  C6H4(C02H)2. 

Orthoxylol  is  a  colorless  liquid,  boiling  at  140-141°.  Nitric 
acid  oxidizes  it  to  orthotoluic  acid. 

Paraxylol  is  solid,  and  crystallizes  in  oblique  rhombic  prisms, 
fusible  at  15°.  It  boils  at  136-137°.  Dilute  nitric  acid  con- 
verts it  into  paratoluie  acid.  Chromic  acid  oxidizes  it  to  ter- 
aphthalic  acid. 

There  are  very  many  derivatives  allied  to  these  isomeric 
xylols.  One  or  more  atoms  of  hydrogen  may  be  replaced, 
either  in  the  benzol  nucleus  or  in  the  methyl  chains,  by  chlo- 
rine, bromine,  or  by  groups  such  as  OH,  NO2,  NH2,  etc.  The 
methyl  chains  may  be  oxidized  by  boiling  the  xylols  with  nitric 
or  chromic  acid,  as  indicated  above.  In  this  case  the  group 
CH3  is  replaced  by  the  carboxyl  group  CO.OH,  and  the  hy- 
drocarbons, C^H^CH3)2,  are  converted  into  either  toluic  acids 
or  phthalic  acids,  of  each  of  which  there  are  three  isomerides. 


CO.OH  CO.OH 

Xylols.  Toluic  acida.  Phthalic  acids. 

We  cannot  describe  all  of  these  bodies  here,  but  must  limit 
ourselves  to  a  brief  description  of  phthalic  acid  and  its  isomer- 
ides. 

PHTHALIC   ACID. 
C8H«0*  =  C«H*(CO.OH)2 

Ordinary,  or  Orthophthalic  Acid.  —  Laurent  obtained  this 
acid  by  boiling  naphthalene  for  a  long  time  with  nitric  acid.  It 
crystallizes  in  brilliant  scales,  or  in  short,  thick  prisms,  which 
are  but  slightly  soluble  in  cold  water,  very  soluble  in  hot  water, 
alcohol,  and  ether.  It  melts  at  213°,  and  loses  the  elements 
of  water  at  a  higher  temperature,  being  converted  into  phthalic 
anhydride. 

54 


638  ELEMENTS   OF   MODERN   CHEMISTRY. 


"2°     +     <«*<co>0 


Phthalic  acid.  Phthalic  anhydride. 

Phthalic  anhydride  crystallizes  in  long,  brilliant  prisms,  fusi- 
ble at  127-128°.  It  boils  at  277°.  It  possesses  a  remarkable 
property,  which  was  discovered  by  A.  Baeyer,  and  which  is  now 
applied  practically  in  the  arts.  When  heated  with  the  phenols, 
it  combines  with  them  directly  with  elimination  of  the  elements 
of  water,  and  compounds  are  obtained  which  are  designated  as 
phthaleins. 

Thus,  when  phthalic  anhydride    is    heated  with  ordinary 
phenol,  two  molecules  of  phenol  combine  with  one  molecule 
of  phthalic  anhydride,  with  elimination  of  one  molecule  of 
water,  and  the  phthalein  of  phenol  is  obtained. 
C6H5.0II    . 


CO-C«H*.OH 


Phthalic  anhydride.         2  inol.  phenol.  Phthalein  of  phenol. 

When  resorcin  is  heated  with  phthalic  anhydride,  two  mol- 
ecules of  water  are  eliminated,  and  a  body  is  obtained  to  which 
Baeyer  has  given  the  name  fluoresceiti. 


Phthalic  anhydride.  2  mol.  resorcin.  Fluorescein. 

Fluorescein  forms  orange-red,  crystalline  grains,  insoluble  in 
cold  water,  and  but  slightly  soluble  in  boiling  water.  It  dis- 
solves readily  in  solutions  of  the  alkalies  and  alkaline  carbonates. 
Its  dilute  solutions  are  yellow,  and  have  a  magnificent  green 
fluorescence.  Hence  the  name  fluorescein. 

Tetrabroino-fluorescein,  C20H8Br4O5,  is  employed  in  dyeing 
under  the  name  eosin.  It  communicates  to  silk  a  beautiful 
rose-red  tint. 

Teraphthalic  Acid  (paraphthalic).  —  Cailliot  obtained  this 
body  by  submitting  oil  of  turpentine  to  a  long  ebullition  with 
dilute  nitric  acid.  The  same  acid  is  formed  by  the  oxidation 
of  paraxylol  and  its  derivatives  by  potassium  dichromate  and 
sulphuric  acid.  It  is  a  white  powder,  almost  insoluble  in  water, 
alcohol,  and  ether.  It  sublimes  without  melting  and  without 
decomposition. 

Isophthalic  Acid  (metaphthalic)  is  formed  by  the  oxidation 
of  metaxylol.  Long,  thin,  colorless  crystals,  slightly  soluble  in 
water,  soluble  in  alcohol,  and  fusible  above  300°.  It  may  be 
sublimed  without  decomposition. 


NAPHTHALENE.  639' 

NAPHTHALENE. 


This  important  compound  was  discovered  by  Garden  in  1820, 
in  coal-tar.  Its  composition  was  determined  by  Faraday,  and 
its  properties  and  transformations  were  principally  studied  by 
Laurent. 

It  is  a  frequent  product  of  the  dry  distillation  of  organic 
matters,  and  is  formed  in  abundance  when  these  matters,  or 
the  products  of  their  decomposition,  are  heated  to  high  tem- 
peratures. Thus  it  is  formed  in  large  quantities  when  tar  is 
passed  through  red-hot  tubes. 

Naphthalene  is  extracted  from  coal-tar,  and  is  purified  by 
crystallization  in  alcohol,  or  by  sublimation. 

Properties.  —  Naphthalene  occurs  in  rhombic  tables  when  it 
has  been  sublimed,  and  is  deposited  in  prisms  from  its  ethereal 
solution.  It  melts  at  79.2°,  and  boils  at  218°.  It  is  inflam- 
mable, and  burns  with  a  very  smoky  flame.  It  is  insoluble  in 
water,  slightly  soluble  in  cold  alcohol,  freely  soluble  in  boiling 
alcohol,  and  very  soluble  in  ether. 

Nitric  acid  attacks  naphthalene,  forming  nitro-  derivatives, 
among  which  is  nitre-naphthalene,  C10H7(N02),  which  crystal- 
lizes in  sulphur-yellow,  rhombic  prisms,  fusible  at  43°.  By 
long  boiling  with  nitric  acid,  naphthalene  is  converted  into 
phthalic  acid,  nitrophthalic  acid,  and  oxalic  acid. 

Chlorine  acts  on  naphthalene  in  two  ways  :  it  combines  di- 
rectly, forming  chlorides  of  naphthalene,  and  produces  numerous 
substitution  products  which  generally  combine  with  an  excess 
of  chlorine. 

Bromine  yields  only  substitution  compounds  with  naphtha- 
lene. 

Among  all  these  products,  we  may  mention  the  following  : 

C10H8C12         naphthalene  dichloride.        C10H*C1    monochloronaphthalene. 
C10H8C14         naphthalene  tetrachloride.  C10H6C12  dichloronaphthalene. 
C10H6C12C14  dichloronaphthalene  tetra-  C10H5C13  trichloronaphthalene. 

chloride. 
C10C18C12        perchloronaphthalene    di-  C10C18       perchloronnphthalene. 

chloride. 

Concentrated  sulphuric  acid  dissolves  naphthalene,  forming 
two  acids  : 

Naphtylsulphurous  acid,        C10H7.S03H 
Naphtyldisulphurous  acid,  C™RG  J 


640  ELEMENTS   OP    MODERN    CHEMISTRY. 

The  formation  of  the  first  of  these  acids  is  expressed  in  the 
following  equation : 

C10H8     +     S04H2    =    H20     +     C10H7.S03H 

Naphthalene.  Naphtylsulphurous  acid. 

NAPHTOL. 
C10H7.OH 

This  body  is  formed  artificially  by  treating  naphthalene  with 
sulphuric  acid,  and  fusing  the  naphtylsulphurous  acid  so  ob- 
tained with  potassium  hydrate  (see  page  606). 

C10H7.S03K      +    KOH    ==    K2S03    +    C10H7.OH 

Potassium  naphtylsulphite.  Naphtol. 

It  forms  silky  needles  or  laminae,  soluble  in  alcohol,  ether, 
and  benzol,  almost  insoluble  in  cold  water,  slightly  soluble  in 
boiling  water.  It  m^lbs  at  94°.  Its  aqueous  solution  produces 
a  violet  color  with  chloride  of  lime. 

An  isomeride  of  naphtol  is  known,  /5-naphtol,  fusible  at  122°, 

NAPHTYLAMINE. 


Zinin  obtained  this  base  in  1842  by  reducing  nitronaphtha- 
lene  by  ammonium  sulphydrate,  which  may  be  advantageously 
replaced  by  iron  and  acetic  acid. 

C10H7(N02)     +     3H2    =    2H20     +     C10H7(NH2) 

Nitronaphthalene.  Naphtylamine. 

It  forms  fine,  colorless  needles.  It  sublimes  at  a  gentle  heat, 
melts  at  50°,  and  boils  without  alteration  at  300°.  It  has  a 
fetid  odor.  Its  reaction  is  not  alkaline,  although  it  perfectly 
neutralizes  the  acids,  with  which  it  forms  well-defined  and 
crystallizable  salts.  When  exposed  to  the  air,  the  salts  of 
naphtylamine  acquire  a  violet  color,  probably  due  to  an  absorp- 
tion of  oxygen. 

ANTHRACENE  AND  PHENANTHRENE. 


Anthracene,  which  is  solid,  exists  in  the  less  volatile  pro- 
ducts of  the  distillation  of  coal-tar.  It  is  obtained  from  the 
last  products  of  this  operation.  The  mass,  which  has  a  buttery 
consistence,  is  squeezed  in  a  filter-press,  and  the  residue  is  sub- 


ALIZARIN.  641 

mitted  to  repeated  distillations  ;  it  is  finally  purified  by  com- 
pression and  several  crystallizations  in  benzol. 

Anthracene  may  be  formed  artificially  by  several  processes, 
especially  by  passing  the  vapor  of  toluol  and  various  derivatives 
of  that  body  through  a  tube  heated  to  bright  redness.  Under 
these  conditions,  two  molecules  of  toluol  lose  six  atoms  of  hy- 
drogen, and  are  converted  into  anthracene. 
C6H5-CH3 


2 

C6JI*=CH 

2  mol.  toluol.  Anthracene. 

In  the  pure  state,  anthracene  forms  rhombic  tables,  derived 
from  an  oblique  rhombic  prism.  The  crystals  are  colorless, 
and  present  a  magnificent  blue  fluorescence  (Fritzsche).  They 
melt  at  213°,  and  distil  without  alteration  at  about  360°. 

By  the  action  of  oxidizing  agents,  such  as  chromic  acid,  an- 
thracene is  converted  into  a  solid  body,  which  crystallizes  in 
beautiful  yellow  needles,  fusible  at  273°,  and  which  can  be 
sublimed  without  alteration.  It  is  anthraquinone^  C14H802,  a 
body  which  bears  the  same  relations  to  anthracene  as  quinone 
to  benzol. 


Benzol.  Anthracene. 

C6H4Q2  CMH80» 

Quinone.  Anthraquinone. 

By  treating  anthraquinone  with  bromine,  Graebe  and  Lieber- 
mann  converted  it  into  dibromanthraquinone,  CuH6Br202,  a 
solid  body,  which  crystallizes  in  yellow  needles. 

Fhenanthrene.  —  Besides  anthracene,  there  is  another  hydro- 
carbon of  the  same  composition,  which  exists  in  coal-tar,  and 
may  also  be  formed  artificially.  It  is  called  phenanthrene,  and 
forms  colorless  scales,  having  a  bluish  fluorescence.  It  melts 
at  100°,  and  boils  at  340°.  It  is  soluble  in  50  parts  of  alco- 
hol at  13°  ;  very  soluble  in  hot  alcohol,  and  in  ether  and 
benzol. 

ALIZARIN. 


Natural  State  and  Synthesis.  —  Alizarin  is  the  name  applied 
to  the  coloring  matter  of  madder  which  llobiquet  was  the  first 
to  extract  in  a  pure  state.  Graebe  and  Liebermann  have  re- 
cently made  its  synthesis  by  heating  dibromanthraquinone  to 
200°  with  potassium  hydrate. 

54* 


642  ELEMENTS   OP   MODERN    CHEMISTRY. 


|_  2KQH  ==  2KBr  -f  C14H6(OH)202 

Dibromanthraquinone.  Alizarin. 

This  reaction,  slightly  modified,  has  become  within  a  few 
years  the  base  of  an  important  industry. 

Alizarin  does  not  exist  ready  formed  in  the  madder  plant. 
The  latter  contains  a  glucoside  to  which  Robiquet  has  given 
the  name  ruberythric  acid,  and  which  is  decomposed  by  the 
action  of  acids  into  alizarin  and  glucose. 

C»H»0M        _|_         2JJ2Q        __         CHH804        _|_         2C6H12()6 
Ruberythric  acid.  Alizarin.  Glucose. 

Preparation,  —  Alizarin  may  be  extracted  from  madder  by 
boiling  the  latter  with  a  solution  of  alum.  The  filtered  liquid, 
left  to  itself  for  some  days,  deposits  impure  alizarin  as  a  brown- 
red  precipitate,  and  holds  in  solution  another  coloring  matter 
which  is  called  purpurin. 

The  precipitated  alizarin  is  purified  by  washing  with  dilute 
hydrochloric  acid,  and  crystallization  in  alcohol.  The  product 
thus  obtained  is  exhausted  with  a  boiling  solution  of  alum, 
which  removes  the  purpurin,  and  is  finally  dissolved  in  ether, 
which  deposits  it  in  crystals. 

To  prepare  artificial  alizarin  from  anthracene,  that  hydro- 
carbon is  first  transformed  into  anthraquinone,  and  the  latter 
body  is  treated  with  sulphuric  acid  to  convert  it  into  disulpho- 
anthraquinonic  acid,  which  is  then  heated  with  an  excess  of 
potassium  hydrate. 

C14H6(SO3K)202  +  2KOH  =  CUH6(OH)202  +  2K*SOS 

Potassium  Alizarin. 

disulphoanthraquinonate. 

The  alkaline  mass  is  dissolved  in  water,  precipitated  by  hy- 
drochloric acid,  and  the  precipitate  purified  by  crystallization 
in  alcohol  and  finally  by  sublimation. 

The  artificial  product  is  delivered  to  commerce  in  the  form 
of  a  paste,  but  the  reaction  by  which  it  is  formed  produces,  at 
the  same  time,  isomerides  which  remain  mixed  with  the  aliza- 
rin, properly  so  called.  Eight  isomeric  compounds  are  known 
having  the  composition  CUH80*.  One  of  them,  purpuroxan- 
thin,  is  contained  in  small  quantity  in  madder. 

Properties  of  Alizarin  —  Alizarin  forms  long,  brilliant, 
orange-yellow  prisms.  It  is  scarcely  soluble  in  cold  water,  but 
dissolves  somewhat  better  in  boiling  water,  and  is  soluble  in 
alcohol,  ether,  and  carbon-disulphide.  Between  215  and  225°, 
it  sublimes  in  long,  orange-yellow  needles.  It  dissolves  in  sul- 


PURPURIN  —  NATURAL   ALKALOIDS,  643 

phuric  acid  with  a  blood-red  color,  and  water  precipitates  it 
without  alteration  from  this  solution.  Boiling  dilute  nitric 
acid  converts  it  into  oxalic  and  phthalic  acids.  When  alizarin 
is  heated  to  redness  with  zinc  powder,  it  is  reduced  to  anthra- 
cene (Graebe  and  Liebermann). 

Alizarin  forms  combinations  with  the  bases  ;  it  dissolves  in 
ammonia,  with  a  purple  color,  and  in  the  caustic  alkalies,  yield- 
ing purple  solutions  which  have  a  blue  reflection. 

Uses.  —  Alizarin  produces  a  red  color  on  fabrics  that  are  mor- 
danted with  alumina,  and  a  violet  on  those  which  are  mor- 
danted with  ferric  oxide.  It  is  the  coloring  principle  of  madder 
and  of  the  commercial  product  known  as  garancin.  The  latter 
product  is  obtained  by  heating  powdered  madder  with  sulphu- 
ric acid  to  100°,  and  exhausting  the  mass  with  water.  The 
residue  is  garancin. 

PURPURIN. 


This  name  is  given  to  another  coloring  matter  which  may  be 
extracted  from  madder,  and  which  has  already  been  mentioned. 
It  appears  to  exist  in  the  plant  as  a  glucoside.  It  dissolves 
readily  in  alcohol  and  ether,  with  a  red  color. 

It  crystallizes  from  weak  alcohol  in  orange-colored  needles, 
which  contain  one  molecule  of  water  of  crystallization.  From 
concentrated  alcohol,  it  deposits  in  red,  anhydrous  needles. 
When  heated,  it  melts  and  sublimes  in  red  needles. 

Purpurin  is  an  oxy  alizarin,  or  a  trioxyanthraquinone,  CUH5 
(OH)3O2  :  indeed,  it  may  be  obtained  by  treating  a  solution  of 
alizarin  in  concentrated  sulphuric  acid  with  an  oxidizing  agent, 
such  as  manganese  dioxide  (de  Lalande).  Inversely,  the  reduc- 
tion of  purpurin  reproduces  alizarin  (Rosenstiehl).  It  under- 
goes a  complete  reduction,  and  is  converted  into  anthracene, 
when  heated  with  zinc-dust. 

Independently  of  the  purpurin  just  described,  there  are  three 
other  compounds  isomeric  with  it. 


NATURAL  ALKALOIDS. 

The  alkaloids  are  nitrogenized  substances  capable  of  uniting 
with  the  acids,  like  ammonia,  and  forming  with  them  definite 
combinations  which  constitute  true  salts.  A  large  number 


644  ELEMENTS   OP   MODERN    CHEMISTRY. 

of  these  compounds  can  be  formed  artificially,  and  are  derived 
directly  from  ammonia  by  the  substitution  of  organic  radicals 
for  the  hydrogen  of  that  body.  They  are  the  compound,  or 
substituted  ammonias,  and  their  constitutions  are  perfectly 
known.  This  is  not,  however,  the  case  with  the  natural  alka- 
loids, which  have  been  discovered  in  many  plants  and  vege- 
table products,  and  which  often  constitute  the  active  principles 
to  which  these  products  owe  their  medicinal  virtues.  By  anal- 
ogy, it  may  be  inferred  that  these  bodies  also  are  derived  from 
ammonia,  like  the  compound  ammonias. 

In  1806,  the  basic  nature  of  one  of  the  crystallizable  princi- 
ples of  opium  was  discovered  by  Serturner,  but  his  discovery 
was  unnoticed  until  181*7,  when  he  published  it  in  a  treatise 
on  morphine.  Among  the  more  important  discoveries  in  this 
class  of  compounds  must  be  mentioned  those  of  strychine, 
brucine,  and  especially  quinine,  discoveries  which  are  due  to 
Pelletier  and  Caventou  (1820). 

All  of  the  alkaloids  contain  nitrogen.  They  are  divided  into 
two  classes,  the  first  of  which  includes  the  liquid  and  volatile 
bases,  and  the  second  the  solids.  The  latter  generally  contain 
oxygen,  the  former  do  not.  The  alkaloids  possess  one  charac- 
teristic property  which  indicates  their  analogy  with  ammonia. 
With  platinic  chloride  their  hydrochlorides  form  double  salts, 
which  are  sometimes  insoluble  in  water,  sometimes  soluble  and 
crystallizable. 

If  a  solution  of  platinic  chloride  be  poured  into  a  solution 
of  quinine  hydrochloride,  a  yellow  precipitate  is  at  once  formed  ; 
it  is  a  combination  of  platinic  chloride  and  quinine  hydrochlo- 
ride, and  is  sometimes  called  quinine  chloroplatinate,  or  platino- 
chloride. 

CONINE. 


This  is  a  liquid  and  volatile  alkaloid  which  is  extracted  from 
the  hemlock  (  Conium  maculatum}.  The  seeds  of  this  tree  are 
crushed  and  distilled  with  sodium  hydrate.  The  alkaline  liquid 
which  collects  in  the  receiver  is  neutralized  by  dilute  sulphu- 
ric acid,  evaporated  to  a  syrupy  consistence,  and  the  residue 
exhausted  with  a  mixture  of  alcohol  and  ether,  which  dissolves 
the  conine  sulphate,  and  leaves  ammonium  sulphate.  The  alco- 
hol and  ether  are  driven  out  by  evaporation  ;  a  concentrated 


NICOTINE.  645 

solution  of  sodium  hydrate  is  added  to  the  conine  sulphate,  and 
the  liquid  is  distilled.  The  conine  passes  with  a  certain  quan- 
tity of  water,  on  which  it  floats.  It  is  separated,  dried  over 
some  fragments  of  calcium  chloride,  and  rectified  in  a  vacuum. 

Conine  is  a  limpid,  oleaginous  liquid,  having  a  penetrating 
and  nauseating  odor,  recalling  that  of  hemlock.  It  boils  at 
168°.  It  is  slightly  soluble  in  water,  more  so  in  cold  than 
in  hot  water,  so  that  a  cold,  saturated  solution  becomes  clouded 
when  heated.  It  is  very  soluble  in  alcohol  and  in  ether.  It 
has  a  strongly  alkaline  reaction,  immediately  restoring  the  blue 
color  to  reddened  litmus-paper.  It  precipitates  many  metallic 
oxides  from  solutions  of  their  salts.  On  contact  with  the  air 
it  becomes  brown  and  resinified. 

Conine  is  often  mixed  with  methylconine,  a  compound  de- 
rived from  conine  by  the  substitution  of  a  methyl  group  for 
an  atom  of  hydrogen  (Planta  and  Kekule). 

Wertheim  has  obtained  from  the  flowers  and  seeds  of  the 
hemlock  a  solid  alkaloid,  which  he  has  named  conhydrine, 
C8H17NO,  and  which  contains  the  elements  of  conine  plus  a 
molecule  of  water. 

Hugo  Schiff  has  recently  made  the  synthesis  of  an  isomeride 
of  conine,  which  he  calls  paraconine. 

NICOTINE. 

C10H14N2 

This  alkaloid  exists  in  tobacco.  It  may  be  obtained  by  ex- 
hausting tobacco  with  boiling  water  and  evaporating  the  liquid 
to  a  syrupy  consistence  on  a  water-bath  ;  the  still  hot  extract 
is  then  mixed  with  twice  its  volume  of  alcohol,  allowed  to  settle, 
and  the  alcoholic  liquid  separated  from  the  thick  lower  layer, 
which  contains  much  calcium  malate.  The  alcohol  is  distilled 
off,  and  the  residue  exhausted  with  strong  alcohol,  of  which 
the  greater  part  is  then  driven  off  by  evaporation.  Potassium 
hydrate  is  added  to  the  alcoholic  extract,  which  is  then  agitated 
with  ether,  which  dissolves  the  nicotine  set  free.  A  few  grammes 
of  oxalic  acid  added  to  the  ethereal  solution  causes  the  separa- 
tion of  a  syrupy  deposit  which  contains  oxalate  of  nicotine. 
This  salt  is  decomposed  by  potassa,  and  the  nicotine  set  free  is 
dissolved  out  by  ether.  After  the  ether  has  been  expelled  on 
a  water-bath,  the  nicotine  is  distilled  in  a  current  of  hydrogen, 
that  part  being  retained  which  passes  above  180°  (Schloesing). 


646  ELEMENTS    OP    MODERN    CHEMISTRY. 

Properties. — Nicotine  is  a  colorless  liquid,  having  an  offen- 
sive, penetrating  odor.  It  rotates  the  plane  of  polarization  to 
the  left.  It  boils  between  240  and  250°,  not,  however,  with- 
out undergoing  partial  decomposition.  Above  146°,  it  begins 
to  distil  slowly,  and  at  100°  it  emits  white  vapors  ;  at  ordinary 
temperatures  it  gives  off  so  much  vapor  that  a  rod  wet  with 
hydrochloric  acid  will  be  enveloped  in  white  fumes  if  held  a 
little  distance  above  the  nicotine. 

Nicotine  dissolves  in  all  proportions  in  water,  alcohol,  and 
ether.  It  has  a  strongly  alkaline  reaction,  and  perfectly  neu- 
tralizes the  acids,  and  precipitates  the  metallic  oxides  from 
solutions  of  their  salts.  It  is  one  of  the  most  violent  poisons 
known. 

ALKALOIDS   OF   OPIUM. 

Opium  is  the  thickened  juice  of  the  capsules  of  the  white 
poppy  (Papaver  somniferum).  It  is  obtained  by  making  in- 
cisions in  these  capsules  from  the  base  to  the  summit.  A  milky 
juice  exudes,  and  in  the  course  of  a  day  thickens  and  solidifies 
in  tears.  These  are  removed,  pressed  together,  and  fashioned 
into  variously-formed  masses. 

Opium  contains  a  number  of  alkaloids  combined  with  several 
acids.  Among  the  latter  are  a  syrupy  acid,  to  which  Ander- 
son gave  the  name  thebolactic  acid,  but  which  has  recently 
been  recognized  to  be  identical  with  lactic  acid  (Buchanan), 
and  meconic  acid,  of  which  the  composition  is  expressed  by 
the  formula  C7H407.  The  latter  is  one  of  the  more  important 
constituents  of  opium ;  it  possesses  the  characteristic  property 
of  producing  a  blood-red  color  with  ferric  salts.  Opium  con- 
tains also  a  gummy  matter,  soluble  in  water,  and  a  brown,  in- 
soluble, resinous  matter,  which  remains  in  the  mass  when 
opium  is  exhausted  with  water.  The  aqueous  solution  of  opium 
has  a  brown  color.  The  following  alkaloids  have  been  obtained 
from  opium : 

Morphine     C^H^NO3 

Codeine        C^J^NO3 

Thebaine      C19H21N03 

Papaverine  C^H^NO* 

Narcotine     C22H23N07 

Narceine      C23H29N09 

Besides  these,  Merck  has  described  another  alkaloid  of  opium 
under  the  name  porphyroxine ;  but,  according  to  Hesse,  this 


MORPHINE.  647 

body  is  a  mixture  of  several  bases,  to  which  he  has  given  the 
names  meconidine,  laudanine,  codamine,  and  lanthopine. 

Opium  sometimes  contains  an  alkaloid  which  is  designated 
as  pseudomachine,  and  which  is  oxymorphine,  C17H19NO4. 

Independently  of  these  alkaloids,  a  neutral,  crystallizable 
substance  has  been  extracted  from  opium,  and  called  meconine, 
C10H1004.  Of  all  these  bodies,  we  will  only  consider  morphine, 
codeine,  and  narcotine. 

MORPHINE. 

C"H19NO3  +  H2O 

Preparation. — 1.  Opium  is  cut  into  slices  and  exhausted 
with  water.  The  solution  is  evaporated  to  a  syrupy  consistence 
and  the  still  hot  extract  is  mixed  with  an  excess  of  pulverized 
sodium  carbonate.  After  the  lapse  of  twenty-four  hours,  the 
precipitate  is  collected  and  exhausted  with  dilute  acetic  acid, 
which  dissolves  the  morphine  and  leaves  the  narcotine.  The 
liquid  is  filtered,  decolorized  by  animal  charcoal,  and  super- 
saturated with  ammonia.  The  morphine  is  precipitated,  and 
is  purified  by  crystallization  in  alcohol  (Merck). 

2.  One  kilogramme  of  opium  is  exhausted  with  cold  water ; 
100  grammes  of  pure  lime  are  added  to  the  liquid,  which  is 
then  evaporated  to  a  syrupy  consistence  at  a  temperature  of  65 
or  75°.  After  cooling,  the  mass  is  exhausted  with  3  litres  of 
water  which  leaves  the  meconate  of  calcium ;  the  latter  is 
separated  by  filtration.  The  liquid  is  then  evaporated  to  one- 
fourth  its  volume,  and  while  it  is  still  hot,  50  grammes  of 
calcium  chloride  dissolved  in  100  grammes  of  water  and  8 
grammes  of  hydrochloric  acid  are  added. 

This  mixture  is  left  to  itself  for  about  two  weeks,  when  it 
will  be  found  to  have  set  in  a  mass  of  crystals  which  are  bathed 
in  a  colored  mother-liquor.  The  deposit  is  pressed  in  a  cloth, 
dissolved  in  boiling  water,  with  addition  of  animal  charcoal, 
and  the  solution  filtered.  On  cooling,  a  mass  of  crystals  ia 
formed,  consisting  of  a  mixture  of  morphine  hydrochloride  and 
codeine  hydrochloride.  These  are  pressed,  dissolved  in  water, 
and  ammonia  is  added,  which  precipitates  the  greater  portion  of 
the  morphine,  while  the  codeine  remains  in  solution.  The 
deposit  is  collected  on  a  filter  and  redissolved  in  boiling  alcohol, 
from  which  the  morphine  crystallizes  on  cooling  (Robertson 
and  Gregory). 


648  ELEMENTS    OF    MODERN    CHEMISTRY. 

Properties. — Morphine  crystallizes  in  small,  colorless,  right 
rhombic  prisms,  having  a  bitter  taste.  It  is  insoluble  in  ether, 
in  chloroform,  and  in  benzol.  The  alcoholic  solution  rotates 
the  plane  of  polarization  to  the  left.  The  crystals  contain  one 
molecule  of  water  which  they  lose  at  100°.  Morphine  dis- 
solves easily  in  a  solution  of  potassium  hydrate ;  it  is  very 
slightly  soluble  in  ammonia ;  almost  insoluble  in  water. 

Tests. — 1.  If  a  few  drops  of  a  solution  of  iodic  acid  be  added 
to  an  alcoholic  solution  of  morphine,  the  liquid  immediately 
assumes  a  brown  or  yellow  color,  due  to  the  liberation  of  iodine. 
Iodic  acid  exerts  an  oxidizing  action  on  morphine. 

2.  If  a  small  quantity  of  morphine  in  powder  be  added  to  a 
solution  of  ferric  chloride,  a  blue  color  is  produced. 

3.  Nitric  acid  produces  an  orange-red  color  with  morphine. 
The  last  two  reactions  are  characteristic. 

When  morphine  is  heated  to  200°  with  potassium  hydrate, 
it  disengages  methylamine. 

Morphine  Hydrochloride. — This  salt,  of  which  the  prepara- 
tion has  already  been  indicated,  crystallizes  in  silky  needles, 
soluble  in  1  part  of  boiling  and  16  or  20  parts  of  cold  water; 
it  is  very  soluble  in  alcohol.  The  crystals  contain  C17H19N03. 
HC1  -f  3H20. 

Platinic  chloride  forms  a  yellow  precipitate  of  a  double  chlo- 
ride in  an  aqueous  solution  of  morphine  hydrochloride. 

(C17H19N03.HCl)2.PtCl4 

Hydrochloride  of  morphine  is  much  used  in  medicine. 

When  its  solution  is  heated  to  60°  with  silver  nitrite,  the 
base  is  oxidized  and  converted  into  oxymorphine,  C17H19NO4. 

When  morphine  is  heated  to  about  140°  with  concentrated 
hydrochloric  acid,  it  is  transformed  into  a  new  base,  apomor- 
phine,  C17H17NO2,  derived  from  morphine  by  the  removal  of 
one  molecule  of  water  (Matthiessen).  This  base  possesses 
special  therapeutic  properties.  When  administered  by  hypo- 
dermic injection  or  swallowed,  it  acts  as  an  emetic. 

CODEINE. 
C18H21NO»  +  H2O 

Codeine  is  methylmorphine.  It  is  obtained  from  the  am- 
moniacal  mother-liquor  from  which  the  morphine  is  deposited, 
in  the  preparation  of  the  latter  body  by  the  process  of  Robert- 


NARCOTINE.  649 

son  and  Gregory.  For  this  purpose,  the  mother-liquor  is  con- 
centrated and  caustic  potassa  is  added,  which  precipitates  the 
codeine.  It  is  collected,  dissolved  in  hydrochloric  acid,  the 
solution  decolorized  with  animal  charcoal,  and  the  codeine  again 
precipitated  by  potassa.  Lastly,  the  precipitate  is  dissolved  in 
ordinary  ether,  which  deposits  the  codeine  in  voluminous  crys- 
tals by  spontaneous  evaporation. 

These  crystals  are  right  rhombic  prisms,  and  contain  one 
molecule  of  water.  Anhydrous  ether  deposits  codeine  in  anhy- 
drous rectangular  octahedra. 

Codeine  dissolves  in  89  parts  of  water  at  15°,  and  is  more 
soluble  in  boiling  water.  Alcohol  and  ether  dissolve  it  readily, 
and  the  alcoholic  solution  rotates  the  plane  of  polarization  to 
the  left. 

If  bromine-water  be  poured  upon  codeine  in  fine  powder, 
the  latter  dissolves,  and  is  converted  into  hydrobromide  of 
monobromo-codeine.  By  the  continued  addition  of  bromine- 
water,  a  yellow  precipitate  is  formed,  consisting  of  hydrobro- 
mide of  tribromo-codeine,  that  is,  codeine  in  which  three  atoms 
of  hydrogen  are  replaced  by  three  atoms  of  bromine. 

NARCOTINE. 


Narcotine  may  be  extracted  from  the  residue  of  opium  which 
has  been  exhausted  by  water.  This  is  treated  with  hydrochloric 
acid,  filtered,  and  the  filtrate  precipitated  by  sodium  carbon- 
ate. The  precipitate  is  dissolved  in  alcohol,  and  the  alcoholic 
solution  decolorized  by  animal  charcoal.  The  narcotine  crys- 
tallizes out  on  cooling. 

It  forms  brilliant,  colorless  prisms,  belonging  to  the  system 
of  the  right  rhombic  prism.  It  melts  at  70°.  It  is  insoluble  in 
cold  water,  and  requires  for  its  solution  about  60  parts  of  cold 
absolute  alcohol,  or  12  parts  of  boiling  absolute  alcohol.  It  is 
soluble  in  ether,  a  character  which  distinguishes  it  from  mor- 
phine. Its  alcoholic  and  ethereal  solutions  have  a  bitter  taste, 
and  turn  the  plane  of  polarization  to  the  left. 

If  a  few  crystals  of  narcotine  in  a  watch-glass  be  moistened 
with  sulphuric  acid  containing  a  trace  of  nitric  acid,  an  intense 
blood-red  color  is  produced. 

By  the  action  of  certain  oxidizing  agents,  narcotine  is  de- 
2c  55 


650  ELEMENTS   OF   MODERN   CHEMISTRY. 

composed  into  a  new  alkaloid,  cotarnine,  and  an  acid  which  is 
called  opianic  acid  (Wbhler). 

C-r2H23NOT     +   o  =     ciogiops      _|_      C12H13N03 

Narcotine.  Opianic  acid.  Cotarnine. 

Cotarnine  crystallizes  in  colorless,  silky  needles,  grouped  in 
stars. 

When  subjected  to  the  action  of  hydriodic  acid,  narcotine 
loses  successively  three  methyl  groups,  and  yields  hydriodides 
of  three  new  bases.  One  of  them  contains  C19H17NOT,  and  has 
been  designated  as  nornarcotine  or  normal  narcotine.  It  is 
formed  according  to  the  equation 

C22H23N07    +     SHI    =    C19H17N07     +     3CIPI 

Narcotine.  Nornarcotine.  Methyl  iodide. 

Hence  narcotine  itself  represents  trimethy I  -  nornarcotine, 
C19HH(CH3)3N07  (Matthiessen  and  Foster).  " 

The  intermediate  terms  between  narcotine  and  nornarcotine 
are  also  known, 

ALKALOIDS   OF   CINCHONA. 

The  different  cinchona  barks  owe  their  febrifuge  virtues  to 
several  alkaloids,  of  which  the  more  important,  quinine  and  cin- 
chonine, were  discovered  by  Pelletier  and  Caventou  in  1820. 
Since  then,  quinidine  and  cinchonidine  have  been  isolated,  the 
first  isomeric  with  quinine,  the  second  with  cinchonine.  All 
of  these  are  crystallizable  alkaloids.  When  their  sulphates  are 
heated  with  sulphuric  acid,  they  are  converted  into  two  new 
isomerides,  quinicine  and  cinchonicine.  The  latter  are  not  crys- 
tallizable. 

Hence  the  following  six  alkaloids  are  known : 

Cinchonine,  cinchonidine,  cinchonicine     .     . 
Quinine,  quinidine,  quinicine 

These  alkaloids  are  by  no  means  distributed  in  the  same 
manner  in  the  numerous  species  and  varieties  of  cinchona  bark, 
and  these  barks  are  not  equally  rich  in  alkaloids.  The  follow- 
ing summary  gives  some  indications  of  this  difference : 

1  KILOGRAMME  OF  BARK  TIELDS  :  QUININE  SULPHATE.  "uL^HATE? 

Yellow  bark  (Cinchona  Calisaya)      .     .  30-32  grammes.  6-8  grammes. 

Red  bark  (Cinchona  snccirubra)    .     .     .  20-25         "  8         " 

("Loxa  (Cinchona  condami- 

Pale  bark    \      nea)     .......            8         "  6 

(Huanuco  (Cinchona  nitida)             6         "  12         " 


QUININE.  651 

In  the  cinchonas,  these  alkaloids  are  combined  with  a  well- 
defined,  crystallizable  acid,  whose  composition  is  expressed  by 
the  formula  C7H1206.  It  is  quinic  acid. 

This  acid  is  obtained  from  the  calcium  quinate  which  is  de- 
posited in  a  few  days,  when  the  liquid  separated  from  the  quino- 
calcium  precipitate  is  concentrated  and  allowed  to  stand  (see 
farther  on). 

This  calcium  quinate  is  purified  by  several  crystallizations, 
and  its  solution  decomposed  by  oxalic  acid.  The  quinic  acid 
remains  in  the  solution,  and  separates  in  crystals  when  the 
liquid  is  properly  concentrated. 

Quinic  acid  crystallizes  in  beautiful,  transparent,  oblique 
rhombic  prisms.  It  is  very  soluble  in  water,  and  but  slightly 
soluble  in  absolute  alcohol.  It  melts  at  161.5°,  losing  at  the 
same  time  the  elements  of  water. 

Its  aqueous  solution  rotates  the  plane  of  polarization  to  the 
left. 

Its  composition  corresponds  to  the  formula  C7H1206.  When 
distilled  with  a  mixture  of  sulphuric  acid  and  manganese  diox- 
ide, it  yields  quinone,  C6H402. 

A  substance  is  also  found  in  cinchona  bark  which  is  called 
quinotannic  acid.  It  belongs  to  the  tannin  group,  and  is  a 
glucoside.  Hlasiwetz  states  that  it  can  be  decomposed  into 
glucose  and  cinchonine  red,  a  substance  noticed  by  Pelletier  and 
Caventou  as  produced  during  the  preparation  of  quinine. 

QUININE. 

C2°H2*N2O2 

When  ammonia  is  added  to  a  solution  of  sulphate  of  quinine, 
a  white  precipitate  of  quinine  is  obtained,  which,  when  left  to 
itself  and  moistened  with  water  from  time  to  time,  becomes 
crystalline  by  combining  with  one  molecule  of  water. 

Quinine  is  very  bitter.  It  dissolves  in  2266  parts  of  cold, 
and  in  760  parts  of  boiling  water ;  in  1.33  parts  of  cold  alco- 
hol, and  22.6  parts  of  ether  (J.  Regnauld).  It  is  also  soluble 
in  chloroform.  Its  alcoholic  solution  turns  the  plane  of  polar- 
ization to  the  left.  When  water  at  32°  is  added  to  the  hot 
alcoholic  solution  until  a  cloud  begins  to  form,  resinous  quinine 
is  deposited,  and  also  colorless,  prismatic  crystals  containing 
three  molecules  of  water. 

Quinine  Sulphate,  2(C20H2*N202).S04H2  +  8H20.— Prep- 


652  ELEMENTS   OF    MODERN    CHEMISTRY. 

ration. — This  salt,  which  is  extensively  used  in  medicine,  is 
prepared  by  boiling  yellow  bark  (Cinchona  Calisaya]  or  red 
bark  (Cinchona  succirubrd)  with  water  acidulated  with  sul- 
phuric or  hydrochloric  acid.  A  slight  excess  of  milk  of  lime 
is  then  added  in  small  quantities  to  the  decoction,  and  precip- 
itates not  only  the  quinine  and  cinchonine,  but  all  of  the  color- 
ing matter  (cinchonine  red),  which  forms  an  insoluble  com- 
pound with  the  lime.  The  quinic  acid  remains  in  solution  as 
calcium  quinate.  The  quino-calcium  deposit  contains  also  the 
excess  of  lime,  and  calcium  sulphate,  in  case  sulphuric  acid 
has  been  employed.  It  is  collected  on  a  cloth,  allowed  to  drain, 
pressed,  and  dried.  It  is  then  exhausted  with  boiling  alcohol, 
which  dissolves  out  the  alkaloids. 

The  alcoholic  solution,  concentrated  by  distillation,  deposits 
the  cinchonine  in  crystals,  in  case  the  bark  employed  be  rich 
in  that  alkaloid.  The  mother-liquor  retains  the  quinine.  It 
is  neutralized  by  sulphuric  acid,  and  the  alcohol  distilled  off. 
The  quinine  sulphate  crystallizes  in  a  mass  on  cooling,  and  is 
purified  by  redissolving  it  in  boiling  water  and  adding  animal 
charcoal. 

It  has  been  proposed  to  replace  the  alcohol,  in  the  extrac- 
tion of  the  quino-calcium  deposit,  by  certain  fixed  or  volatile 
oils,  which  dissolve  quinine.  For  this  purpose,  petroleum  and 
the  heavy  oils  produced  by  the  distillation  of  tar,  and  which  are 
abundant  in  commerce,  may  be  used  with  advantage.  After 
having  dissolved  the  alkaloids  in  these  oils,  the  solutions  are 
agitated  with  dilute  sulphuric  acid,  which  removes  from  them 
the  quinine  and  cinchonine.  Sulphates  are  thus  obtained  which 
may  be  crystallized. 

Properties. — Quinine  sulphate  occurs  in  long,  thin,  light 
needles,  which  are  somewhat  flexible.  It  requires  for  its  solu- 
tion 740  parts  of  water  at  13°,  or  about  30  parts  of  boiling 
water.  The  solution  restores  the  blue  color  to  reddened  litmus- 
paper.  It  turns  the  plane  of  polarization  to  the  left  (Bouchar- 
dat).  When  crystallized  in  alcohol,  quinine  sulphate  contains 
only  two  molecules  of  water. 

If  some  quinine  sulphate  be  suspended  in  cold  water,  and  a 
few  drops  of  sulphuric  acid  be  added,  the  sulphate  dissolves 
and  the  liquid  acquires  a  blue  fluorescence. 

In  this  case,  quinine  sulphate,  which  is  a  basic  salt,  is  con- 
verted into  a  salt,  C'^H^OISO4!!2,  which  has  an  acid  reac- 
tion, and  is  called  quinine  acid  sulphate.  This  salt  crystallizes 


CINCHONINE.  653 

with  7  molecules  of  water.     A  still  more  acid  sulphate  is  known, 
C"H14N*OI.(SOtH8)1  -f  m20. 

If  an  excess  of  chlorine-water  be  added  to  a  solution  of 
quinine  sulphate,  and  the  liquid  be  supersaturated  with  ammo- 
nia, a  beautiful  green  color  will  be  produced. 

This  reaction  is  characteristic  of  quinine. 

When  tincture  of  iodine  is  added  to  a  solution  of  quinine 
sulphate  in  hot  acetic  acid,  in  a  few  hours  the  liquid  deposits 
large,  thin  plates.  It  is  iodoquinine  sulphate,  C20H24N202F. 
S04H2  -f  5IFO  (Herapath). 

These  crystals  appear  green  by  reflected  light,  and  are  almost 
colorless  by  transmitted  light.  When  two  of  them  are  crossed, 
the  portions  which  are  superposed  almost  entirely  intercept  the 
passage  of  light.  In  this  respect,  iodoquinine  sulphate  acts 
as  a  polarizer,  like  tourmaline. 

Uses.  —  Quinine  sulphate  is  a  valuable  remedy.  It  is  prin- 
cipally employed  as  a  febrifuge,  and  generally  in  the  treatment 
of  diseases  of  an  intermittent  type.  It  is  successfully  admin- 
istered in  other  diseases,  especially  in  acute  articular  rheuma- 
tism, gout,  certain  neuralgias,  etc. 

CINCHONINE. 


Cinchonine  is  obtained  as  an  accessory  product  in  the  manu- 
facture of  quinine.  It  deposits  from  its  alcoholic  solution  in 
brilliant,  colorless,  quadrilateral  prisms.  It  is  insoluble  in 
water,  but  soluble  in  alcohol  and  chloroform.  It  is  almost 
insoluble  in  ether,  a  property  which  distinguishes  it  from  qui- 
nine. Its  alcoholic  solution  turns  the  plane  of  polarization  to 
the  right. 

Cinchonine  has  a  bitter  taste.  It  melts  at  1*70°,  and  when 
cautiously  heated  in  the  bottom  of  a  closed  tube,  it  partly  sub- 
limes in  very  light,  delicate  crystals.  When  treated  with  a 
dilute  solution  of  potassium  permanganate,  it  forms  various 
substitution  products,  and  a  new  base  remains,  less  oxidizable 
than  cinchonine.  It  is  hydrocinchonine.  Caventou  and  Willm 
consider  that  this  base  is  contained,  in  the  state  of  mixture,  in 
commercial  cinchonine. 

By  oxidizing  cinchonine  with  nitric  acid,  Weidel  has  ob- 
tained a  series  of  acids,  one  of  which  contains  nine  atoms  of 
carbon  ;  it  is  quinolic  acid,  C9H6N204,  while  two  others  contain 


654  ELEMENTS    OF    MODERN   CHEMISTRY. 

each  eleven  atoms.  Lastly,  the  fourth  of  these  acids,  cinchonic. 
acid,  has  the  composition  C20HWN204.  When  distilled,  it  yields 
a  non-nitrogenized  acid,  C10H1005,  pyrocinchonic  acid,  which  is 
an  isomeride  of  opianic  acid. 

STRYCHNINE  AND  BRUCINE. 

Pelletier  and  Caventou  discovered  these  two  alkaloids  in 
various  vegetable  products  derived  from  plants  belonging  to  the 
genus  Strychnos,  such  as  nux  vomica  (seeds  of  the  Strychnos 
Nux  vomica),  false  angustura  bark,  which  comes  from  the  same 
Strychnos,  Saint  Ignatius  bean  (seeds  of  the  Strychnos  Ignatii}, 
etc.  These  alkaloids,  to  which  igasurine  has  recently  been 
added  (Desnoix),  appear  to  be  combined  in  the  Strychnos  with 
an  acid  but  little  known,  which  Pelletier  and  Caventou  called 
iaasuric  acid. 

Strychnine,  CMHBN20*. — Preparation. — Strychnine  is  ex- 
tracted from  nux  vomica  by  a  process  analogous  to  that  which 
serves  for  the  preparation  of  quinine.  The  crude  strychnine 
which  deposits  in  crystals  from  its  alcoholic  solution  is  always 
mixed  with  brucine..  The  two  alkaloids  are  separated  by  con- 
verting them  into  nitrates,  which  are  made  to  crystallize ;  the 
strychnine  nitrate,  less  soluble  than  that  of  brucine,  deposits 
in  needles,  and  the  concentrated  solution  afterwards  deposits 
voluminous  crystals  of  brucine  nitrate.  To  isolate  the  alka- 
loids, the  corresponding  nitrates  are  precipitated  by  ammonia, 
and  the  alkaloid  dissolved  in  boiling  alcohol,  which  deposits  it 
in  crystals  on  cooling. 

Properties. — Strychnine  crystallizes  in  rectangular  octa- 
hedra,  sometimes  in  quadrilateral  prisms  terminated  by  four- 
sided  pyramids.  It  is  colorless  and  odorless,  but  extremely 
bitter.  It  is  insoluble  in  water  and  in  ether,  and  scarcely 
soluble  in  absolute  alcohol.  It  dissolves  readily  in  ordinary 
alcohol,  in  chloroform,  and  in  the  volatile  oils.  Its  alcoholic 
solution  turns  the  plane  of  polarization  to  the  left. 

Strychnine  is  one  of  the  most  active  poisons  known ;  even 
in  very  small  doses  it  produces  violent  tetanic  spasms. 

Brucine,  C23H26N204  -f  4H20.— Brucine,  separated  from 
strychnine  by  the  process  above  indicated,  crystallizes  by  slow 
evaporation  of  its  solution  in  weak  alcohol  in  oblique  rhombic 
prisms,  which  are  often  quite  large.  These  crystals,  which 
contain  four  molecules  of  water,  rapidly  effloresce  in  the  air. 


COCAINE  —  ACONITINE.  655 

Brucine  is  almost  insoluble  in  water,  but  dissolves  readily  in 
alcohol  and  very  slightly  in  ether.  The  alcoholic  solution  ro- 
tates the  plane  of  polarization  to  the  left. 

If  brucine  be  moistened  with  nitric  acid,  it  immediately 
assumes  a  blood-red  color  and,  by  the  aid  of  a  gentle  heat, 
disengages  carbon  dioxide  and  vapors  which  contain  methyl 
nitrite  (Strecker). 

COCAINE. 


Cocaine  was  obtained  by  Niemann  from  coca  leaves  (Ery- 
ihroxylon  Coed].  It  has  been  studied  by  Wohler  and  Lassen. 

Preparation.  —  Coca  leaves  are  exhausted  several  times  with 
water  at  a  temperature  between  60  and  80°,  and  the  solu- 
tion is  precipitated  by  lead  acetate,  and  filtered  ;  the  filtered 
solution  is  freed  from  excess  of  lead  acetate  by  addition  of 
sodium  sulphate  and  then,  after  a  new  filtration,  the  solution 
is  evaporated.  Sodium  carbonate  is  then  added  until  it  pro- 
duces a  faint  alkaline  reaction  ;  the  liquid  is  lastly  agitated 
with  ether,  which  takes  up  the  cocaine  and  leaves  it  on  evapo- 
ration. 

Properties.  —  Cocaine  crystallizes  in  oblique  rhombic  prisms 
of  four  or  six  sides,  which  are  colorless  and  odorless,  and  fuse 
at  98°.  It  is  but  slightly  soluble  in  cold  water,  more  soluble  in 
alcohol,  very  soluble  in  ether.  Its  taste  is  bitter,  its  reaction 
slightly  alkaline.  When  heated  with  hydrochloric  acid,  it  ab- 
sorbs two  molecules  of  water  and  decomposes  into  methyl  alco- 
hol, benzoic  acid,  and  a  crystallizable  base,  ecgonine.  C9H15N03 
-f  H20. 

CnH2iN04  _j_  2H20  =  C»H15N03  +  CH40  -f  C7H602 

ACONITINE. 


The  Aconitum  Napellm  contains,  independently  of  aconitic 
acid,  a  base  which  was  extracted  by  Geiger  and  Hesse.  It 
occurs  as  a  white  powder,  or  as  colorless,  tabular  crystals,  only 
slightly  soluble  in  water,  very  soluble  in  alcohol.  Its  taste  is 
acrid  and  bitter.  It  is  a  violent  poison.  Its  nitrate  crystal- 
tizes  readily.  v 


656  ELEMENTS    OF    MODERN    CHEMISTRY. 

ATROPINE. 


This  alkaloid,  which  is  largely  used  in  the  treatment  of  dis- 
eases of  the  eyes,  was  discovered  in  1833  by  Geiger  and  Hesse, 
and  by  Mein,  in  the  belladonna,  or  deadly  nightshade  (Atropa 
Belladonna).  Planta  has  shown  the  identity  of  atropine  and 
daturine,  which  has  been  obtained  from  the  thorn-apple 
(Datura  Stramonium). 

Preparation.  —  Belladonna-root  is  reduced  to  powder  and 
digested  several  days  with  alcohol.  The  solution  is  filtered, 
slaked  lime,  in  quantity  equal  to  one-twentieth  of  the  weight  of 
root  employed,  is  added,  the  solution  again  filtered,  and  rendered 
slightly  acid  with  sulphuric  acid.  It  is  again  filtered,  and  f  of 
the  alcohol  distilled  off.  The  residue  is  concentrated  at  a  gentle 
heat,  and  a  concentrated  solution  of  potassium  carbonate  is  added 
until  the  liquid,  now  neutral,  begins  to  be  clouded.  After  a  few 
hours,  the  precipitate  is  separated  by  filtration,  and  potassium 
carbonate  is  added  to  the  filtrate  as  long  as  impure  atropine  is 
precipitated.  The  next  day,  the  deposit  is  collected  on  a  filter, 
pressed,  dried,  and  exhausted  with  96  per  cent,  alcohol.  The 
solution  is  decolorized  with  animal  charcoal,  the  liquid  diluted 
with  five  or  six  times  its  volume  of  water  and  put  in  a  cool, 
dark  place.  The  atropine  is  deposited  in  12  or  24  hours  in 
crystalline  needles. 

Properties.  —  Atropine  crystallizes  in  delicate  needles,  fusi- 
ble at  90°.  It  dissolves  in  300  parts  of  cold  water,  and  in 
almost  all  proportions  of  alcohol.  It  is  less  soluble  in  ether. 
At  140°  it  volatilizes,  but  the  greater  part  of  it  is  decomposed. 

In  burning,  atropine  diffuses  the  odor  of  benzoic  acid.  When 
it  is  treated  with  potassium  dichromate  and  sulphuric  acid, 
benzyl  aldehyde  distils  and  benzoic  acid  is  formed  (Pfeiffer). 

Atropine  is  a  virulent  poison.  A  solution  of  sulphate  of 
atropine  is  used  in  medicine.  A  single  drop,  even  of  a  very 
dilute  solution  of  this  salt,  produces  dilatation  of  the  pupil. 

THEOBROMINE. 


Theobromine  exists  in  the  beans  of  the  cacao  (  Theobroma 
Cacao).     To  prepare  it,  the  crushed  cacao  beans  are  exhausted 


CAFFEINE  —  ALBUMINOID    MATTERS.  65*7 

with  water,  and  the  aqueous  extract  is  precipitated  by  lead  ace- 
tate. The  precipitate  is  separated  by  filtration,  and  the  filtrate 
is  freed  from  an  excess  of  lead  by  hydrogen  sulphide  ;  it  is  then 
again  filtered,  and  evaporated  to  dryness.  The  residue  is  dis- 
solved in  absolute  alcohol  and  the  solution  concentrated  ;  the 
theobromine  separates  as  a  crystalline  powder,  having  a  bitter 
taste,  slightly  soluble  in  alcohol  and  ether.  It  may  be  sublimed. 
It  is  soluble  in  ammonia. 

CAFFEINE,  OR   THEINE. 
H*0 


Caffeine  was  extracted  from  coffee  in  1821  by  Pelletier  and 
Caventou,  and  by  Robiquet  and  Runge.  Liebig,  Pfaff,  and 
Wohler  determined  its  composition.  It  exists  in  coffee,  tea, 
Paraguay  tea  (leaf  of  the  Ilex  Paragnaiensis^  and  guarana 
(seeds  of  the  Paidlinia  Sorbilis}.  The  latter  product  contains 
5  per  cent.  Caffeine  is  methyl-theobrouiine. 

Preparation.  —  Caffeine,  or  theine,  is  generally  obtained 
from  tea.  Powdered  tea  is  exhausted  several  times  with  cold 
alcohol,  and  the  tincture  is  precipitated  by  subacetate  of  lead, 
filtered,  and  a  current  of  hydrogen  sulphide  passed  through 
the  filtrate  to  precipitate  the  excess  of  lead.  The  filtered  liquid 
is  then  evaporated  to  one-fourth  its  volume,  neutralized  by  po- 
tassium hydrate,  and  allowed  to  crystallize  (Herzog). 

Properties.  —  Caffeine  forms  long,  silky  needles,  which  are 
light  and  colorless.  It  loses  its  water  of  crystallization  at  100°, 
melts  at  178°,  and  sublimes  without  alteration  at  a  higher  tem- 
perature. It  is  only  slightly  soluble  in  cold  water,  but  dissolves 
readily  in  boiling  water,  and  in  alcohol.  It  is  but  slightly  soluble 
in  ether.  It  forms  definite  combinations  with  the  acids.  When 
boiled  with  concentrated  potassa,  it  disengages  methylamine. 

When  caffeine  is  boiled  for  a  few  minutes  with  fuming  nitric 
acid,  the  yellow  liquid  evaporated  to  dryness,  and  the  residue 
moistened  with  ammonia,  a  purple  color  is  produced,  analogous 
to  that  of  murexide. 


ALBUMINOID    MATTERS. 

The  albuminoid  matters  are  complex  organic  substances,  con- 
taining carbon,  hydrogen,  oxygen,  and  nitrogen,  which  are  often 
associated  with  a  small  proportion  of  sulphur.  By  their  com- 


658  ELEMENTS   OP   MODERN   CHEMISTRY. 

position  and  properties  they  are  allied  to  the  coagulable  matter 
which  exists  in  white  of  egg  and  in  the  serum  of  blood,  and 
which  is  called  albumen. 

The  epidermic  productions  and  the  insoluble  substances 
which  are  converted  into  gelatin  or  chondrin  by  boiling,  differ 
from  albumen  and  its  allied  compounds  by  their  composition. 
They  contain  less  carbon  and  more  nitrogen.  For  this  reason 
the  neutral  nitrogenized  matters  of  the  economy  are  divided 
into  two  comprehensive  classes,  albuminoid  substances  proper, 
and  those  substances  which  resemble  in  composition  the  insol- 
uble matter  which  forms  the  cartilage  of  bones,  and  which 
yield  gelatin  by  the  action  of  boiling  water. 

The  more  important  of  the  albuminoid  bodies  are  as  follows : 

Albumen  ...  A  nitrogenized  matter,  coagulable  by  heat,  and  exist- 
ing in  many  liquids  of  the  animal  economy,  particu- 
larly in  white  of  egg  and  the  serum  of  blood. 

Fibrin  ....  A  nitrogenized  matter,  which  deposits  in  the  solid  state 
during  the  coagulation  of  blood. 

Casein  ....  A  nitrogenized  matter,  existing  in  milk,  and  considered 
identical  with  albuminate  of  sodium. 

Globulin  ...  An  albuminoid  substance  that  can  be  obtained  from 
the  red  blood-corpuscles. 

Syntonin  .  .  .  An  albuminoid  substance,  resulting  from  the  action  of 
very  dilute  hydrochloric  acid  on  muscular  fibres. 

Myosin  ....     An  albuminoid  body  contained  in  muscular  fibres. 

Vitellin  ....     The  albuminoid  matter  of  yolk  of  egg. 

Hemoglobin  .  .  A  crystallizable  substance  contained  in  red  blood-cor- 
puscles. 

Among  the  cartilaginous  and  gelatinous  substances  are  the 
following : 

O^sein,  or  collagene,  which  forms  the  cartilage  of  bones,  and  yields  gelatin 

when  boiled  with  water. 
Chondrogin,  which  constitutes  the  cartilage  of  the  short  ribs,  and  which 

yields  chondrin  when  boiled  with  water. 
Keratin,  or  horny  structure. 
Elastin,  the  constituent  of  elastic  tissue. 
Fibroin,  a  product  peculiar  to  silk-worms,  etc. 

The  substances  belonging  to  these  two  groups  possess  the 
following  elementary  composition : 

FIRST   GROUP.  SECOND   GROUP. 

Carbon 53.5  50.0 

Hydrogen 6.9  6.6 

Nitrogen 15.6  16.8 

Oxygen 23  to  22.4  26.1  to  23.1 

Sulphur 1  to    1.6  0.5  to    3.5 


100.0  100.0 


ALBUMINOID    MATTERS.  659 

Of  most  of  the  albuminoid  substances,  two  modifications 
are  known,  one  soluble  and  the  other  insoluble.  Thus  heat, 
acids,  and  alcohol  convert  soluble  albumen  into  insoluble  albu- 
men, and  the  latter  appears  to  have  the  same,  or  very  nearly 
the  same  composition  after  coagulation  as  before. 

The  insoluble  albuminoid  bodies,  such  as  coagulated  albu- 
men, cooked  albumen,  fibrin,  and  casein,  dissolve  by  the  aid  of 
a  gentle  heat  in  potassium  hydrate,  to  which  they  yield  a 
portion  of  their  sulphur.  The  alkaline  liquid,  supersatu- 
rated with  acetic  acid,  precipitates  the  dissolved  matter  in 
flakes. 

Concentrated  and  boiling  solutions  of  the  alkalies  decompose 
all  albuminoid  substances,  the  principal  products  of  the  decom- 
position being  carbon  dioxide,  formic  acid,  gtycocol,  and  its 
homologue  leucine,  C6H13N02,  as  well  as  a  nitrogenized  sub- 
stance known  as  tyrosine  and  containing  C9HnN03.  The  other 
decomposition  products  will  be  indicated  when  treating  of 
albumen. 

Leucine  and  tyrosine  are  also  formed  when  albuminoid  sub- 
stances are  long  boiled  with  dilute  sulphuric  acid.  At  the  same 
time,  aspartic  acid,  and  glutamic  acid,  C5H9N04,  which  is  the 
acid  amide  of  normal  pyrotartaric  acid,  is  formed. 


^. 
<C02H 

Pyrotartaric  acid.  Glutamic  acid. 

Concentrated  hydrochloric  acid  dissolves  the  insoluble  albumi- 
noid bodies,  and  the  solution  assumes  a  violet  color,  especially 
on  contact  with  the  air  (Caventou). 

When  brought  into  contact  with  water  containing  one  or 
two  thousandths  of  hydrochloric  acid,  insoluble  albuminoid  mat- 
ters swell  up  and  are  finally  converted  into  a  transparent  jelly, 
which  partially  dissolves  in  water. 

By  the  action  of  energetic  oxidizing  agents,  such  as  chromic 
acid,  or  manganese  dioxide  and  sulphuric  acid,  albuminoid 
bodies  produce  various  products  of  Oxidation  and  decomposi- 
tion, among  which  we  may  note  particularly:  (1),  the  volatile 
acids  of  the  series,  CnH2n02,  from  formic  acid  to  caproic  acid 
inclusive  ;  (2),  the  corresponding  aldehydes  ;  (3),  the  nitriles 
(hydrocyanic  ethers),  propionitrile  (ethyl  cyanide),  and  valero- 
nitrile  (butyl  cyanide)  ;  (4),  benzoic  acid  and  benzyl  alde- 
hyde. 


660  ELEMENTS   OP   MODERN   CHEMISTRY. 


ALBUMEN. 

Two  modifications  of  albumen  are  known :  one  is  soluble, 
the  other  insoluble. 

Soluble  albumen  exists  in  solution  in  white  of  egg,  and  in 
other  liquids  of  the  animal  economy.  The  coagulable  prin- 
ciple of  the  serum  of  blood  is  a  liquid  very  analogous  to  the 
albumen  of  white  of  egg ;  some  chemists  have  called  it  serin. 

When  a  filtered  solution  of  white  of  egg  is  evaporated  at  a 
low  temperature  or  in  a  vacuum,  the  soluble  albumen  at  length 
dries  to  a  transparent,  yellowish  mass,  having  a  gummy  appear- 
ance. In  this  state  it  is  not  pure  ;  it  remains  combined  with 
a  trace  of  alkali  and  mixed  with  a  small  quantity  of  salts. 
When  treated  with  water,  it  again  dissolves.  When  it  is  per- 
fectly dry,  it  may  be  heated  to  even  1 00°  without  losing  all  of 
its  water.  The  greater  part,  if  not  all,  of  the  salts  which  exist 
in  white  of  egg  with  the  albumen  may  be  removed  by  dialysis 
(Graham). 

When  a  solution  of  white  of  egg  or  of  the  serum  of  blood 
is  heated,  the  liquid  begins  to  be  clouded  at  70°,  and  coagulates 
at  about  73°,  sometimes  in  flakes,  sometimes  in  a  white  mass, 
according  to  the  concentration  of  the  solution ;  heat  converts 
albumen  into  the  insoluble  variety. 

When  white  of  egg  is  diluted  with  eight  or  nine  times  its 
volume  of  water  and  the  carbonic  acid  gas  which  is  dissolved 
or  combined  with  the  albumen  is  carefully  expelled  at  a  low 
temperature,  a  solution  is  obtained  which  is  not  coagulable  by 
heat.  The  lost  property  may,  however,  be  restored  by  passing 
carbon  dioxide  through  the  liquid. 

It  is  generally  considered  that  there  is  no  difference  of  com- 
position between  soluble  and  insoluble  albumen.  However, 
Schiitzenberger  finds  that  the  difference  is  sensible.  If  strong 
alcohol  be  added  to  a  solution  of  albumen,  a  white  coagulum  is 
formed,  which  becomes  insoluble  in  water  by  the  prolonged 
action  of  alcohol. 

Action  of  Acids  on  Albumen. — Sulphuric,  hydrochloric,  and 
nitric  acids  precipitate  albumen  in  thick  flakes,  which  retain  a 
certain  quantity  of  acid ;  the  latter  may  be  removed  by  pro- 
longed washings  with  water. 

The  action  of  nitric  acid  upon  albumen  is  often  used  for  the 
detection  of  that  substance  in  pathological  urine.  A  still  more 


ALBUMEN.  661 

sensitive  reagent  is  metaposphoric  acid,  which  precipitates  the 
smallest  traces  of  albumen  contained  in  a  solution. 

Ordinary  phosphoric  acid,  acetic  acid,  and  lactic  acid,  do  not 
precipitate  solutions  of  albumen. 

Action  of  Alkalies  on  Albumen. — When  white  of  egg  is 
beaten  up  with  a  few  drops  of  a  very  concentrated  solution  of 
potassium  hydrate,  it  sets  in  a  few  minutes  in  a  soft,  trans- 
parent, semi-solid  mass,  from  which  the  excess  of  potassa  may 
be  removed  by  washing  with  cold  water.  The  residue  is  albu- 
minate  of  potassa,  from  which  all  of  the  excess  of  potassa  may 
be  removed  by  prolonged  washings.  This  gelatinous  albumi- 
nate  of  potassa  dissolves  in  boiling  water.  Acetic  acid  precip- 
itates the  albumen  from  the  solution. 

When  potassa  is  added  to  a  solution  of  albumen,  albuminate 
of  potassa  is  formed  in  the  same  manner ;  acetic  acid  precip- 
itates the  albumen,  which  it  renders  insoluble,  but  the  alkaline 
solution  is  not  troubled  by  boiling.  If  a  few  drops  of  lead 
acetate  be  added  to  the  liquid,  the  oxide  of  lead  formed  will 
remain  dissolved  in  the  excess  of  alkali,  'the  liquid  then 
blackens  on  boiling,  for  the  sulphur  contained  in  the  albumen 
acts  on  the  lead,  forming  lead  sulphide. 

Insoluble  albumen  dissolves  in  the  alkalies  and  alkaline  car- 
bonates, forming  albuminates. 

Albumen  combines  with  calcium  hydrate,  as  with  potassa ; 
a  mixture  of  white  of  egg  and  slaked  lime  constitutes  a  very 
hard  cement. 

By  subjecting  albumen  and  its  analogues  to  the  action  of 
an  aqueous  solution  of  barium  hydrate  at  a  temperature  of  140 
or  150°,  Schiitzenberger  observed  that  these  bodies  decompose, 
by  hydration,  into  ammonia,  carbon  dioxide,  oxalic,  sulphurous, 
and  acetic  acids  (the  latter  three  bodies  in  very  small  propor- 
tion), and  into  other  products,  which  are  mostly  crystalliza- 
ble.  These  products  are  tyrosine  and  the  acid  amides  of  the 
fatty  series  CnH2imNOa,  from  amidobutyric  acid,  C4H7(NH2)02, 
to  amid-oenanthic  acid,  C7H13(NH2)02,  inclusive.  With  these 
products  are  others  which  are  also  crystallizable,  but  contain 
less  hydrogen ;  lastly,  more  highly  oxidized  amides  are  formed 
in  the  same  reaction,  such  as  malamic,  diamidocitric,  aspartic, 
and  glutamic  acids. 

From  these  results,  it  may  be  inferred  that  albumen  and  its 
analogues  contain  the  elements  of  urea,  tyrosine,  acid  amides 
of  the  fatty  series,  and  more  oxidized  amides  analogous  to  as- 

56 


662  ELEMENTS   OF   MODERN   CHEMISTRY. 

partic  acid,  all  of  these  bodies  being  combined  together,  with 
elimination  of  water.  The  presence  of  a  certain  proportion  of 
a  dextriniform  body  in  the  products  of  the  decomposition  of 
albumen  permits  the  supposition  that  the  complex  molecule  of 
the  latter  body  contains  also  an  amide  of  cellulose  or  an  amy- 
laceous body. 

Action  of  the  Salts  on  Albumen. — Many  salts  precipitate 
solutions  of  albumen.  Acetate  and  subacetate  of  lead  form 
dense  precipitates  of  albuminate  of  lead.  Cupric  sulphate  pro- 
duces a  blue  precipitate.  Corrosive  sublimate  yields  a  white 
precipitate,  even  in  very  dilute  solutions  of  albumen.  The  in- 
solubility of  this  precipitate  explains  the  use  of  albumen  as  an 
antidote  to  corrosive  sublimate. 

Solutions  of  albumen  are  not  precipitated  by  solutions  of 
sodium  chloride  or  sodium  sulphate,  but  when  acetic  acid  is 
added  to  the  mixture,  a  precipitate  forms.  Reciprocally,  a  solu- 
tion of  albumen  to  which  acetic  acid  has  been  added  is  pre- 
cipitated by  solutions  of  sodium  chloride  and  sodium  sulphate 
(Panum). 

When  incinerated,  both  soluble  and  insoluble  albumen  leave 
a  residue  of  calcium  phosphate  from  which  it  is  almost  impos- 
sible to  free  the  albumen. 

FIBRIN. 

When  recently-drawn  blood  is  left  to  itself,  it  coagulates 
spontaneously  in  a  few  minutes,  and  soon  separates  into  a  yel- 
low liquid  called  the  serum,  and  a  red  coagulum,  which  is  the 
dot.  The  clot  contains  the  red  corpuscles,  imprisoned  in  an 
insoluble  albuminoid  matter.  This  matter  is  fibrin,  and  it  is 
now  considered  to  be  formed  during  the  coagulation  at  the  ex- 
pense of  two  soluble  substances,  both  of  which  exist  in  solution 
in  the  liquid  portion  of  blood,  which  is  called  plasma.  One  of 
these  substances  is  called  fibrinogen,  the  other  is  the  fibrino- 
plastic  matter  or  paraglobulin.  These  two  bodies  have  been 
isolated :  when  they  are  mixed  in  presence  of  water  and  a 
certain  proportion  of  sodium  chloride,  the  whole  dissolves  at 
first  and  the  liquid  soon  coagulates  spontaneously ;  the  coagu- 
lum is  fibrin  (Hoppe-Seyler). 

However  this  may  be,  fibrin  may  be  obtained  in  fibrous 
masses  by  beating  fresh  blood.  The  latter  does  not  coagulate 
in  this  case,  but  the  coagulable  constituent  attaches  itself  in 


MYOSIN.  663 

red  flakes  to  the  rods  with  which  the  blood  is  agitated.  By 
washing  these  flakes  in  running  water,  they  are  freed  from  the 
adhering  red  corpuscles,  and  obtained  in  white  or  grayish  elas- 
tic masses  of  a  fibrous  appearance.  This  substance  is  entirely 
insoluble  in  pure  water,  but  dissolves  in  slightly  alkaline  solu- 
tions, and  even,  by  the  aid  of  a  gentle  heat,  in  solutions  of 
certain  salts  which  have  an  alkaline  reaction.  It  decomposes 
hydrogen  dioxide  into  oxygen  and  water. 

When  left  to  itself  during  the  heat  of  summer,  it  putrefies 
very  rapidly,  and  is  converted  into  a  blackish  liquid,  which 
contains  albumen.  Leucine,  and  butyric  and  valeric  acids  are 
formed  at  the  same  time. 

When  treated  with  concentrated  hydrochloric  acid,  fibrin 
dissolves,  forming  a  blue  solution.  When  still  moist  fibrin  is 
introduced  into  water  containing  one  or  two  thousandths  of 
concentrated  hydrochloric  acid,  it  swells  and  becomes  trans- 
parent, forming  a  jelly.  After  some  time  it  dissolves  in  the 
liquid,  although  with  difficulty,  and  the  solution  then  contains 
a  substance  which  appears  to  be  identical  with  syntonin  (see 
farther  on). 

When  fibrin,  swollen  by  hydrochloric  acid,  is  digested  at 
about  40°  with  gastric  juice,  or  with  the  ferment  called  pepsin, 
which  may  be  obtained  from  that  liquid,  the  fibrin  entirely  dis- 
solves and  is  converted  into  a  soluble  and  dialyzable  body  called 
peptone.  This  body  is  formed  during  the  digestion  of  albu- 
minoid matters. 

Under  certain  circumstances  sodium  chloride  dissolves  fibrin. 
When  such  a  solution  is  dialyzed,  the  salt  passes  into  the  exte- 
rior liquid,  and  there  remains  in  the  dialyzer  a  limpid  solution 
having  all  the  characters  of  a  solution  of  albumen  from  egg 
(A.  Gautier). 

MYOSIN. 

Kuhne  has  designated  by  this  name  the  albuminoid  matter 
which  exists  in  solution  in  the  sheaths  of  the  muscular  fibres 
(sarcolemma),  and  which  has  the  property  of  coagulating  spon- 
taneously after  death,  thus  producing  cadaveric  rigidity. 

Myosin  is  insoluble  in  water  as  well  as  in  a  saturated  solu- 
tion of  common  salt,  but  it  dissolves  in  a  solution  containing 
ten  per  cent,  of  salt.  It  may  be  extracted  from  the  muscles 
by  the  following  process :  the  flesh  is  chopped  up,  and  decolor- 
ized by  washing  with  water ;  it  is  then  triturated  with  pul- 


664  ELEMENTS   OF    MODERN   CHEMISTRY. 

verized  common  salt,  and  enough  water  is  added  to  produce  a 
10  per  cent,  solution  of  salt.  After  digestion  for  a  few  hours 
in  the  cold,  the  liquid  is  filtered  and  brought  into  contact  with 
rock  salt ;  as  the  latter  dissolves,  it  precipitates  the  myosin  in 
flakes. 

Recently-precipitated  myosin  dissolves  in  a  ten  per  cent, 
solution  of  salt,  but  it  loses  this  property  by  desiccation.  Very 
dilute  hydrochloric  acid  dissolves  it,  and  soon  transforms  it 
into  syntonin. 

SYNTONIN. 

This  substance  may  be  extracted  from  muscular  tissue.  The 
latter  is  hashed,  washed  with  water,  and  suspended  in  a  large 
quantity  of  water  containing  one-thousandth  of  hydrochloric 
acid.  The  particles  of  meat  swell  and  dissolve  abundantly  in 
the  liquid,  which  is  then  pressed  through  a  cloth,  filtered,  ana 
exactly  neutralized  with  sodium  carbonate.  The  syntonin  is 
precipitated  in  gelatinous,  colorless  flakes,  which  collect  and 
dry  upon  the  filter  in  elastic  films. 

Syntonin  dissolves  in  water  slightly  acidulated  with  hydro- 
chloric acid.  It  also  dissolves  in  lime-water,  and  in  a  one  per 
cent,  solution  of  sodium  carbonate. 

HEMOGLOBIN. 

This  name  is  given  to  the  crystalline  matter  which  may  be 
extracted  from  red  blood-corpuscles,  and  which  was  first  called 
Jiematocrystalline. 

Preparation. — Clotted  blood  is  broken  up  and  triturated 
with  its  own  volume  of  water  until  it  is  entirely  reduced.  It 
is  then  passed  through  a  cloth,  and  the  liquid  is  frozen,  or 
agitated  with  small  quantities  of  ether  until  the  corpuscles  are 
dissolved.  The  thawed  liquid,  or  that  which  has  been  treated 
with  etlrer,  deposits  a  coagulum  which  imprisons  all  of  the 
unbroken  corpuscles.  The  liquid  is  filtered,  rendered  slightly 
acid  by  acetic  acid,  and  alcohol  is  added  as  long  as  the  pre- 
cipitate first  formed  continues  to  dissolve.  When  cooled  to  0° 
for  several  hours,  the  red  liquid  sets  in  a  mass  of  crystals ; 
these  are  collected  on  a  filter,  pressed,  and  washed  with  dilute 
alcohol  and  water,  both  at  0°.  They  are  purified  by  dissolving 
them  in  water  at  40°  and  evaporating  the  solution  in  a  vacuum, 
or  by  adding  alcohol  and  cooling  the  liquid  to  0°. 


HEMOGLOBIN. 


665 


Composition. — Hemoglobin  so  prepared  has  about  the  same 
composition  as  albuminoid  bodies,  but  contains  a  little  iron. 
According  to  Hoppe-Seyler,  its  composition  is 

Carbon 54.18 

Hydrogen 7.2 

Nitrogen 16.2 

Oxygen 21.5 

Iron 0.42 

Sulphur 0.7 

Properties. — Hemoglobin  forms  crystals  which  differ  accord- 
ing to  the  blood  from  which  they  have  been  obtained.     They 
generally  belong   to   the  type 
of   the  right  rhombic   prism. 
Those  from  human  blood  pre- 
sent, under  the  microscope,  the 
forms  indicated  in   Fig.   132. 
They  are  red,  and  doubly  re- 
fracting.    They  contain  water 
of  crystallization. 

They  dissolve  in  water,  and 
more  readily  in  slightly  alkaline 
solutions. 

The  red  solution  of  hemo- 
globin (oxyhemoglobin)  has 
an  important  optical  property. 
When  light  which  has  trav- 
ersed a  dilute  notation  of  hemo- 
globin is  decomposed  by  a 
prism,  the  spectrum  so  formed  shows  two  black  bands  (absorp- 
tion bands)  between  Fraunhofer's  lines  D  and  E  (Stokes). 

The  crystals  of  hemoglobin  contain  oxygen  which  is  weakly 
combined,  and  which  may  be  removed  by  exposing  the  crys- 
tals in  a  vacuum  (Hoppe-Seyler).  Oxygenated  hemoglobin  is 
known  as  oxyhemoglobin,  and  hemoglobin  deprived  of  oxygen 
reabsorbs  that  gas  when  brought  into  contact  with  it.  It  is 
curious  that  carbon  monoxide  will  expel  the  oxygen  from  hemo- 
globin, at  the  same  time  replacing  it  (Cl.  Bernard).  The  com- 
bination of  hemoglobin  and  carbon  monoxide  is  soluble  in 
water. 

The  solution  of  oxyhemoglobin  yields  its  oxygen  to  certain 
reducing  agents,  such  as  hydrogen  sulphide.  Reduced  hemo- 
globin gives  an  absorption  spectrum  containing  one  single  band, 

66* 


FIG.  132. 


666  ELEMENTS   OP   MODERN   CHEMISTRY. 

situated  in  a  position  between  the  two  absorption-bands  of  oxy- 
hemoglobin. 

Hemoglobin  decomposes  hydrogen  dioxide.  It  is  very  un- 
stable, and  if  the  crystals  be  dried  at  a  temperature  above  100° 
they  rapidly  become  altered.  The  aqueous  solution  decom- 
poses spontaneously  in  a  few  hours  at  15°,  or  temperatures 
above  that  point.  The  acids,  even  the  weak  ones,  favor  this 
decomposition,  which  is  manifested  by  a  change  of  color,  the 
fine  red  tint  of  the  hemoglobin  being  replaced  by  a  brown.  In 
these  cases,  hemoglobin  decomposes  into  an  albuminoid  matter 
(globulin),  and  a  ferruginous  pigment  called  hematin.  At  the 
same  time,  small  quantities  of  fatty  acids  are  set  free  (Hoppe- 
Seyler). 

Hematin. — This  substance  has  received  different  names. 
Lecauu,  who  first  studied  it,  named  it  hematosin.  When  prop- 
erly purified,  it  forms  a  blackish-blue,  amorphous  powder,  which 
is  quite  stable,  since  it  resists  a  temperature  of  180°.  It  con- 
tains carbon,  hydrogen,  nitrogen,  oxygen,  and  iron.  When 
incinerated,  it  leaves  12.8  per  cent,  of  oxide  of  iron. 

It  is  insoluble  in  water,  alcohol,  ether,  and  chloroform.  It 
dissolves  in  the  alkalies,  in  ammonia,  and  in  the  acids,  and  is 
readily  soluble  in  ammoniacal  alcohol  and  in  alcohol  containing 
hydrochloric  acid.  These  solutions  are  reddish-brown.  With 
hydrochloric  acid,  hematin  forms  a  compound  which  crystallizes 
in  rhomboidal  laminae ;  the  crystals  are  characteristic  and  may 
be  recognized  by  means  of  the  microscope  (hydrochloride  of 
hematin). 

Hematoidin. —  This  body  is  doubtless  a  product  of  the 
decomposition  of  hemoglobin.  Virchow  found  it  in  orange- 
colored  crystals  in  the  remains  of  old  hemorrhages  of  the  brain. 
It  is  also  found  in  blood  which  has  been  exposed  to  air,  and  in 
extravasated  blood  in  the  Graefian  follicles.  It  may  easily  be 
obtained  from  the  yellow  bodies  contained  in  the  ovaries  of  the 
cow,  by  triturating  them  with  glass,  and  digesting  for  a  few 
days  with  chloroform.  After  evaporation  of  the  yellow  chloro- 
form solution,  the  residue  is  treated  with  ether  to  dissolve  out 
the  fat. 

Hematoidin  crystallizes  in  small,  orange-red,  transparent 
prisms.  It  is  insoluble  in  water  and  alcohol,  slightly  soluble 
in  ether ;  it  is  soluble  in  chloroform,  which  it  colors  golden- 
yellow.  It  presents  certain  analogies  with  bilirubin  (page 
673). 


GLOBULIN — CASEIN — GELATIN.  667 


GLOBULIN. 

Berzelius  gave  this  name  to  the  coagulable  albuminoid  sub- 
stance which  may  be  obtained  from  red  blood-corpuscles,  and 
which  is  now  believed  to  be  a  product  of  the  decomposition  of 
hemoglobin.  This,  or  an  analogous  substance,  exists  in  the 
crystalline  lens.  It  may  be  obtained  by  boiling  the  crystalline 
lens  of  the  ox  with  water  and  filtering  the  liquid.  A  solution 
of  globulin  is  thus  obtained.  It  much  resembles  albumen  in 
its  properties.  When  heated,  it  becomes  clouded  at  73°,  but 
coagulates  completely  only  at  93°.  It  is  not  precipitated  by 
either  acetic  acid  or  by  the  alkalies,  but  when  its  acid  or 
alkaline  solution  is  neutralized,  a  precipitate  is  formed.  A 
solution  of  globulin  is  precipitated  by  a  current  of  carbon  di- 
oxide. 

CASEIN. 

When  an  acid  is  added  to  milk,  a  thick  precipitate  is  at  once 
formed ;  it  is  produced  by  the  casein.  The  lactic  acid  which 
forms  in  milk  by  the  fermentation  of  the  milk-sugar,  produces 
the  same  precipitation.  The  milk  is  then  said  to  curdle.  The 
precipitate  consists  of  an  albuminoid  matter  called  casein, 
which  is  considered  to  be  identical  with  coagulated  albumen. 

Casein  dissolves  in  alkaline  liquids  and  even  in  certain  alka- 
line salts,  such  as  carbonate  and  phosphate  of  sodium.  It 
exists  in  this  state  in  milk,  which  is  alkaline  when  fresh. 
When  this  solution  of  alkaline  albuminate,  to  which  the  name 
soluble  casein  has  been  given,  is  evaporated,  it  becomes  covered 
with  a  pellicle.  Acetic  acid  precipitates  it  in  flakes,  combining 
with  the  alkali.  It  is  also  coagulated  by  the  gastric  juice, 
which  is  acid,  and  which  contains  a  ferment  known  as  pepsin. 
This  ferment  exists  in  rennet  which  is  prepared  from  the 
fourth  stomach  of  the  calf,  and  which  serves  to  coagulate 
skimmed  milk  in  the  preparation  of  cheese.  Indeed,  casein, 
more  or  less  altered  by  putrefaction,  is  the  basis  of  the  different 
kinds  of  cheese. 

GELATIN. 

The  bones  contain  a  cartilaginous  substance,  which  may  be 
isolated  by  dissolving  out  the  mineral  salts,  which  consist  of 
calcium  carbonate  and  phosphate,  with  hydrochloric  acid. 


668  ELEMENTS   OP    MODERN    CHEMISTRY. 

There  remains  a  semi-transparent,  elastic  substance,  which  re- 
tains the  form  of  the  bone.  This  substance,  which  has  been 
called  ossein,  or  collagene,  is  insoluble  in  cold  water,  but  by 
prolonged  boiling,  or  more  rapidly  by  digestion  with  water 
heated  to  a  few  degrees  above  100°,  it  dissolves  and  forms  a 
solution,  which  sets  in  a  transparent  jelly  on  cooling.  The 
body  formed  by  this  transformation  dissolves  slightly  in  cold 
water,  and  abundantly  in  boiling  water,  and  the  hot  solution 
forms  a  jelly  on  cooling.  Hence  the  name  gelatin. 

Other  tissues  of  the  animal  economy  may  be  converted  into 
gelatin  by  boiling  with  water.  It  is  so  with  the  cellular  tissue, 
the  skin,  the  scales,  and  swimming-bladder  of  fishes.  The 
swimming-bladder  of  the  sturgeon,  known  in  commerce  as  fish- 
glue,  furnishes  very  pure  gelatin  by  boiling  with  water. 

The  substances  which  may*be  converted  into  gelatin  possess 
very  nearly  the  same  composition  as  gelatin  itself;  hence  no- 
thing precise  is  known  concerning  the  nature  of  the  change 
produced  in  them  by  the  action  of  boiling  water. 

Dry  gelatin  occurs  in  transparent  sheets,  which  are  sonorous, 
and  of  which  the  color  varies  from  yellowish  to  brown,  accord- 
ing to  their  thickness  and  purity. 

The  aqueous  solution  is  precipitated  in  white  flakes  by  alco- 
hol. The  acids  do  not  precipitate  it,  with  the  exception  of 
tannic  acid,  with  which  it  forms  a  thick  coagulum,  a  combina- 
tion of  tannin  and  gelatin.  This  action  of  tannin  on  gelatinous 
matters  is  applied  in  the  manufacture  of  leather,  which  is  ob- 
tained by  leaving  fresh  or  green  skins,  previously  swelled  by 
soaking  in  water,  in  contact  with  tan,  that  is,  coarsely-ground 
oak-bark,  which  is  well  known  to  contain  tannin. 

When  chlorine-water  is  added  to  a  solution  of  gelatin,  a 
white  cloud  is  formed  which  an  excess  of  chlorine  converts 
into  a  white,  flocculent  precipitate. 

Solutions  of  gelatin  are  precipitated  by  platinic  chloride 
and  by  corrosive  sublimate,  but  not  by  alum  or  the  salts  of  lead, 
copper,  silver,  etc.  When  boiled  with  dilute  sulphuric  acid, 
gelatin  is  converted  into  leucine  and  a  substance  to  which 
Braconnot  gave  the  name  sugar  of  gelatin,  and  which  is  gly- 
cocol. 

Chondrin. — When  the  cartilages  of  the  short  ribs  are  boiled 
for  a  very  long  time  with  water,  they  dissolve,  forming  a  liquid 
which  sets  in  a  jelly  on  cooling.  This  gelatinous  matter  is 
chondrin.  It  is  distinguished  from  gelatin  by  the  property  of 


RESPIRATION.  669 

its  aqueous  solution  to  form  precipitates  with  all  the  acids,  and 
with  a  great  number  of  metallic  salts.  Alum  forms  in  it  an 
abundant,  flocculent  precipitate. 


The  substances  which  have  just  been  summarily  described, 
and  others  which  form  the  liquids  an  dtissues  of  the  animal 
economy,  undergo  various  transformations  in  the  organism. 
They  are  derived  from  the  vegetable  kingdom,  which  alone  can 
elaborate  such  complex  matters.  They  pass  with  the  aliments 
into  the  animal  organisms,  which  assimilate  them,  and  this  work 
of  assimilation  does  not  profoundly  modify  the  nitrogenized 
matters.  But  once  fixed  in  the  tissues,  they  do  not  remain 
there  indefinitely,  for  there  is  a  continual  change  and  renewal 
of  the  whole  economy.  They  become  unfitted  for  the  require- 
ments of  life,  and  disappear  in  their  turn,  eliminated  by  that 
continual  oxidation  which  makes  of  the  body  a  permanent 
hearth  of  slow  combustion.  A  notable  portion  of  the  oxygen 
which  enters  the  lungs  at  each  inhalation  penetrates  into  the 
blood,  and  is  converted  in  the  capillary  system  and  the  intrica- 
cies of  the  tissues  into  carbon  dioxide.  This  gas,  which  returns 
to  the  lungs  with  the  venous  blood,  is  exhaled  at  each  exhala- 
tion. Expired  air  contains  4  to  5  per  cent,  of  carbon  dioxide. 

The  carbon  dioxide  eliminates  the  greater  portion  of  the 
carbon  contained  in  the  organic  bodies  burned  during  the  phe- 
nomenon of  respiration.  The  hydrogen  of  these  bodies  is 
eliminated  in  the  form  of  water.  But  what  becomes  of  their 
nitrogen  ?  In  man,  and  a  great  number  of  the  higher  animals, 
it  is  eliminated  in  the  urea  contained  in  the  urine.  Such  are 
the  principal  features  of  this  grand  function  of  respiration,  the 
source  of  heat  in  all  animals. 

But  how  is  this  slow  oxidation  which  constitutes  the  object 
of  respiration,  as  first  shown  by  Lavoisier,  accomplished  ?  Are 
the  organic  matters  ready  to  be  oxidized  and  consumed  at  once, 
or  does  the  oxidation  take  place  in  successive  phases,  so  that 
there  are  a  certain  number  of  intermediate  terms  between  the 
complex  products  which  must  disappear  and  the  final  products 
of  their  oxidation  ?  All  facts  lead  to  the  adoption  of  the  latter 
conclusion.  Indeed,  there  are  found  in  the  tissues  and  liquids 
of  the  economy  a  great  number  of  bodies  having  compositions 
more  or  less  complex,  and  which  are  the  products,  and,  as  it 


670  ELEMENTS    OF    MODERN    CHEMISTRY. 

were,  the  testimony  of  a  successive  simplification,  —  of  disas- 
Rimilation,  as  it  is  called. 

But  it  must  not  be  supposed  that  all  of  the  reactions  which 
take  place  in  the  economy  are  phenomena  of  oxidation.  Be- 
fore being  definitely  oxidized  and  rejected  from  the  body,  the 
ingested  organic  matters  and  those  which  form  our  humors  and 
tissues,  may  undergo  various  transformations  and  sometimes 
molecular  complications.  In  this  respect,  Dr.  Ure's  celebrated 
experiment  is  well  known  :  having  taken  benzoic  acid,  he  found 
hippuric  acid  in  his  urine.  Analysis  has  shown  the  presence 
in  the  animal  economy  of  a  multitude  of  more  or  less  complex 
organic  compounds,  nitrogenized  and  non-nitrogenized,  having 
definite  compositions,  and  which  are  the  products  of  varied 
reactions.  Such  reactions  take  place  in  the  blood  and  in  the 
tissues,  principally  in  glandular  organs,  such  as  the  liver.  As 
it  would  be  impossible  to  consider  all  of  these  products  of  dis- 
assimilation,  we  can  only  briefly  notice  the  more  important. 

LECITHINE. 


Grobley  has  given  this  name  to  a  phosphorized  fatty  matter, 
before  noticed  in  the  brain  by  Vauquelin.  It  exists  in  the 
brain  and  in  the  nerves.  There  is  a  closely  allied  body,  recently 
described  by  Liebreich,  under  the  name  protagon. 

Grobley  extracted  lecithine  from  yolk  of  egg.  That  substance 
is  exhausted  with  a  mixture  of  alcohol  and  ether,  and  an  alco- 
holic solution  of  cadmium  chloride  is  added  to  the  solution 
obtained  ;  a  white,  flocculent  precipitate  is  formed,  and  is  puri- 
fied by  washing  with  alcohol  and  ether.  This  precipitate  is  a 
compound  of  cadmium  chloride  and  hydrochloride  of  lecithine. 
It  is  suspended  in  ether  and  decomposed  by  hydrogen  sulphide  : 
cadmium  sulphide  is  precipitated  and  hydrochloride  of  lecithine 
remains  in  solution,  and  may  be  obtained  on  evaporation  in  a 
wax-like  mass.  When  the  alcoholic  solution  of  this  hydro- 
chloride  is  decomposed  by  silver  oxide,  the  lecithine  is  set  free, 
and  remains,  after  evaporation,  in  the  form  of  a  homogeneous, 
translucent  mass.  Lecithine  may  also  be  precipitated  by  pla- 
tinic  chloride  instead  of  cadmium  chloride  (Strecker). 

Lecithine  and  all  of  its  compounds  are  very  alterable.  It 
decomposes  rapidly  when  the  alcoholic  solution  of  its  hydro- 
chloride  is  boiled  with  baryta-water  ;  oleate  and  palmitate  of 


CHOLESTERIN.  671 

barium  are  precipitated,  phosphoglycerate  of  barium  is  formed, 
and  an  organic  base  called  neuriiie  remains  in  solution  (Lieb- 
reich). 

Strecker  represents  this  interesting  decomposition  by  the 
equation 


3H2Q   =    C3IFP06    +    C5R15N02 

Lecithine.  Phospho-  Neurine.  Oleic  Palmitic 

glyceric  acid.  acid.  acid. 

Neurine  is  an  oxygenized  base  of  which  the  constitution  is 
known.  It  is  the  hydrate  of  trimethyl-hydroxethylene-ammo- 
nium  (page  527). 

(C2H>.OH)'  )  „ 


The  chloride  of  this  ammoniated  base  is  formed  by  synthesis 
by  the  action  of  ethylene  chlorohydrate  on  trimethylamine  (A. 
Wurtz). 


Trimetliyl-hydroxethylene- 
auimuniuiu  chloride. 


Neurine  is  identical  with  a  base  which  Strecker  obtained 
from  the  bile  and  designated  as  cholme. 

CHOLESTERIN. 


This  body  is  largely  diffused  in  the  organism.  It  exists  in 
the  bile,  and  is  the  principal  constituent  of  most  biliary  cal- 
culi. It  is  found  also  in  small  quantity  in  the  serum  of  blood, 
in  the  brain,  in  yolk  of  egg,  pus,  the  liquid  of  hydrocele,  etc. 

Its  solubility  in  alcohol  and  especially  in  ether,  and  the 
facility  with  which  it  crystallizes  from  its  solutions,  permits 
its  easy  isolation.  Cholesterin  ordinarily  deposits  in  thin  and 
brilliant,  rhombic  plates.  It  melts  at  145°,  and  can  be  sub- 
limed, out  of  contact  with  air,  at  360°. 

It  forms  neutral  compounds  with  acids,  analogous  to  the 
ethers  ;  it  seems  to  be  a  monatomic  alcohol. 


The  principal  organic  constituents  of  the  bile  are  two  com- 
plex acids,  both  nitrogenized,  and  one  of  which  contains  sul- 
phur. These  are  glycocholic  and  taurocholic  acids.  They  are 


672  ELEMENTS   OF    MODERN   CHEMISTRY. 

not  contained  in  the  bile  of  all  animals,  and  are  generally  ex- 
tracted from  that  of  the  ox.  They  enter  into  the  composition 
of  human  bile,  which  contains  in  addition  coloring  matters 
of  which  the  most  important  is  bilirubin.  We  will  briefly 
describe  these  bodies. 

GLYCOCHOLIC   ACID. 


This  body  exists  in  the  bile  in  the  form  of  sodium  glycocho- 
late,  which  salt  may  be  obtained  in  crystals  from  ox's  bile. 
The  latter  is  decolorized  by  animal  charcoal,  filtered,  the 
liquid  evaporated,  and  the  residue  perfectly  dried  and  dissolved 
in  absolute  alcohol  ;  the  solution  is  introduced  into  a  flask,  and 
ether  is  cautiously  added  so  that  the  two  liquids  may  not  mix, 
but  form  two  layers.  The  latter  gradually  mingle  and  the 
sodium  glycocholate  deposits  in  crystals  (Plattner). 

When  dilute  sulphuric  acid  is  added  to  a  solution  of  this 
salt,  a  cloud  is  formed,  and  glycocholic  acid  is  soon  deposited 
in  fine  needles. 

This  acid  is  only  slightly  soluble  in  water  and  ether,  but  dis- 
solves in  alcohol.  It  is  dextrogyrate  (Hoppe-Seyler).  By  the 
action  of  hydrochloric  acid,  it  is  decomposed  into  cholalic  acid 
and  glycocol  (Strecker). 

C26H43N06     _|_     H20    =     C24H4<,05     +     C2H5N02 

Glycocholic  acid.  Cholalic  acid.  Glycocol. 

Cholalic  Acid  exists  in  the  amorphous  state  and  crystallized. 
It  deposits  from  its  ethereal  solution  in  four-sided  prisms, 
beveled  at  the  ends,  and  containing  two  molecules  of  water  of 
crystallization.  By  boiling  with  acids,  it  is  converted  into  a 
resinous  body  which  Berzelius  called  dy  sly  sin. 

C24H4o05    ^     C24H3603     +     2H20 

Dyslysin. 

TAUROCHOLIC  ACID. 

C26H*5NSO7 

The  sodium  salt  of  this  acid  remains  dissolved  in  the  ethe- 
real solution  from  which  sodium  glycocholate  has  deposited. 
It  has  not  yet  been  obtained  crystallized.  It  is  dextrogyrate. 
When  boiled  with  dilute  acids,  or  with  alkalies,  it  breaks  up 
into  cholalic  acid  and  taurine  (Strecker). 


BILIRUBIN— BILIVERDIN.  673 

C26H45NS07     +     H20    =    C^H^O5    +     C2HTNS03 

Taurocholic  acid.  Cholalic  acid.  Tauriiie. 

Taurine,  which  was  discovered  by  Leopold  Grmelin,  has 
already  been  described  (page  528). 

BILIRUBIN. 
C16H18N203 

This  substance  exists  in  human  bile  and  in  biliary  calculi. 
It  may  be  extracted  from  the  latter,  which  contain  it  as  calcu- 
lary  pigment.  They  are  crushed,  and  exhausted,  first  with 
ether,  which  removes  the  cholesterin,  then  with  boiling  water, 
and  finally  with  chloroform.  The  coloring  matter  remains  in 
the  residue  as  a  calcareous  combination ;  this  is  decomposed 
by  adding  hydrochloric  acid,  evaporating  to  dryness,  and  ex- 
hausting the  dried  residue  with  chloroform.  After  evaporation, 
the  chloroform  solution  leaves  a  residue  which  contains,  inde- 
pendently of  bilirubin,  three  other  biliary  pigments  which  we 
will  only  mention  :  biliprasin,  bilifuscin,  and  bilihumin.  Alco- 
hol dissolves  the  bilifuscin  from  this  residue,  and  the  new 
residue  is  exhausted  with  chloroform,  which  takes  up  the  bili- 
rubin, which  alcohol  precipitates  in  orange-colored  flakes  from 
the  chloroform  solution. 

Bilirubin  is  obtained  in  small,  dark-red  crystals  by  evapora- 
tion of  its  solution  in  chloroform.  It  is  insoluble  in  water,  and 
very  slightly  soluble  in  ether  and  alcohol,  but  dissolves  in  chlo- 
roform, benzol,  and  carbon  disulphide.  It  is  very  soluble  in 
the  alkalies,  forming  an  orange-red  solution,  which  becomes 
pure  yellow  on  addition  of  water,  and  from  which  hydrochloric 
acid  precipitates  bilirubin.  The  ammoniacal  solution  of  bili- 
rubin gives  precipitates  with  calcium  chloride,  barium  chloride, 
and  lead  acetate. 


BILIVERDIN. 


When  a  solution  of  bilirubin  in  sodium  hydrate  is  agitated 
with  air,  it  absorbs  oxygen  and  becomes  green.  Hydrochloric 
acid  precipitates  biliverdin  from  the  solution. 

It  is  a  bright  green  powder,  insoluble  in  water,  ether,  and 
chloroform,  but  soluble  in  alcohol.  It  contains  one  more  atom 
of  oxygen  than  bilirubin. 

2D  57 


674  ELEMENTS   OP   MODERN   CHEMISTRY. 

We  may  add  that  other  coloring  matters  have  also  been 
derived  from  bile.  They  are  bilifuscin,  C16H20N204,  biliprasin, 
CMHMN»08,  and  bilihumin. 

CREATINE. 

C*H»N«02  +  H2Q 

This  body  was  discovered  by  Chevreul  in  meat  broth.  It 
exists  ready  formed  in  the  muscles,  and  passes  into  the  extract 
of  meat.  It  may  be  prepared  by  treating  the  solution  of  this 
extract  with  basic  acetate  of  lead,  filtering,  freeing  the  filtrate 
from  excess  of  lead  by  hydrogen  sulphide,  and  evaporating  the 
solution  at  a  gentle  heat  until  it  crystallizes.  The  crystals  are 
separated  from  the  mother-liquor,  and  alcohol  added  to  the 
latter  precipitates  a  fresh  quantity  of  creatine  (Neubauer.) 

Creatine  crystallizes  in  brilliant,  colorless,  oblique  rhombic 
prisms,  containing  one  molecule  of  water,  which  they  lose  at 
100°,  becoming  opaque. 

By  the  action  of  acids  or  by  long  boiling  with  water,  crea- 
tine is  converted  into  creatinine. 

C4H9N3Q2    =    c4H7N30     +    H20 

Creatine.  Creatinine. 

When  creatine  is  boiled  with  baryta-water,  it  is  converted 
into  sarcosine,  ammonia  being  disengaged  and  barium  carbon- 
ate precipitated  at  the  same  time.  It  is  generally  considered 
that  the  ammonia  and  carbon  dioxide  are  produced  in  this  case 
at  the  expense  of  urea,  which  is  formed  directly  by  the  decom- 
position of  creatine. 

C4H9N302     +     H20    =±    C3H7N02    +     CH4N20 

Creatine.  Sarcosine.  Urea. 

Sarcosine  is  methylglycocol.  It  is  isomeric  with  lactamide 
and  alanine.  It  may  be  obtained  artificially  by  treating  mono- 
chloracetic  acid  with  methylamine  (Volhard.) 

C2H2C10.0H     +     CH3.NH2    =    C»H20<^(CH8)  +     HC1 

Monochloracetic  acid.    Methylamine.  Sarcosine. 

Volhard  has  made  the  synthesis  of  creatine  by  the  action  of 
cyanamide  on  sarcosine.  Cyanamide,  CN.NH2,  represents  am- 
monium cyanate  less  the  elements  of  water. 

CN2H2    +     C3H7N02    =     C4!PN302 

Cyanamide.  Sarcosine.  Creatine. 


CREATININE.  675 

CREATININE. 
OH'NH) 

This  body  exists  in  muscular  tissue  independently  of  creatine. 
It  may  be  precipitated  from  the  mother-liquor  from  which  the 
latter  body  has  deposited,  by  adding  an  alcoholic  solution  of 
zinc  chloride,  which  forms  a  crystalline  combination  with  the 
creatinine. 

Creatinine  crystallizes  in  oblique  rhombic  prisms.  It  is  much 
more  soluble  in  alcohol  than  creatine.  It  has  basic  properties, 
and  forms  a  crystallizable  compound  with  hydrochloric  acid. 

Creatine  and  creatinine  have  been  found  not  only  in  the 
muscles,  but  in  small  quantities  in  the  brain,  blood,  and  urine. 


Among  the  products  of  disassimilation  we  may  also  mention  : 

Leucine,  C6H13N02,  which  belongs  to  the  homologous  series 
of  glycocol,  and  is  found  in  many  organs,  especially  in  the 
pancreas,  the  salivary  glands,  the  spleen,  and  the  liver  (page 
546). 

Tyrosine,  C9HnN03,  a  body  crystallizing  in  fine  needles 
may  be  obtained  from  the  pancreas  and  the  spleen  (page  631). 

It  is  known  also  that  leucine  and  tyrosine  may  be  obtained 
directly  by  the  action  of  alkalies  upon  complex  nitrogenized 
matters  (page  661). 

Hippuric  acid,  C9H9N03,  the  origin  of  which  has  already 
been  indicated  (page  62*7). 

Uric  acid,  C5H4N*03,  which  exists  in  small  quantity  in 
human  urine,  and  which  constitutes  a  large  proportion  of  the 
urine  of  birds  and  reptiles  (page  559). 

Allantoin,  C4H6N403,  a  product  of  the  oxidation  of  uric  acid, 
which  Vauquelin  and  Buniva  formerly  extracted  from  the  am- 
niotic  liquor  of  the  cow,  and  which  has  also  been  found  in  the 
urine  of  young  calves  (page  563). 

Various  other  products  are  related  to  uric  acid.     They  are : 

Xanthine,  C5H4N402,  a  yellow  matter,  which  Proust  discov- 
ered in  certain  rare  calculi  (xanthic  calculi),  and  which  has 
also  been  found  in  small  quantity  in  the  muscles,  pancreas,  liver, 
and  urine. 

57* 


676  ELEMENTS   OF   MODERN    CHEMISTRY. 

Hypoxanthine  or  sarcine,  C5H4N40,  a  white,  amorphous  sub- 
stance which  Scherer  obtained  from  the  spleen,  and  of  which 
Strecker  has  noticed  the  existence  in  muscular  tissue.  Hypo- 
xanthine forms  a  crystallizable  combination  with  hydrochloric 
acid.  It  presents  interesting  relations  of  composition  with  xan- 
thine  and  uric  acid. 

Uric  acid  ,     .     .     C5H*N*03 

Xanthine CSHWO* 

Hypoxanthine C5H*N*0 

When  hypoxanthine  is  boiled  with  nitric  acid,  it  is  converted 
into  a  nitrogenized  body.  By  the  action  of  reducing  agents, 
such  as  ferrous  sulphate,  this  nitrogenized  body  is  converted 
into  guanine,  C5H5N30.  The  latter  body  was  first  obtained 
from  guano.  It  has  been  found  in  the  tissue  of  the  pancreas. 


MEASURES   OF  WEIGHT. 


1  Milligramme 
1  Centigramme 
1  Decigramme 
1  Gramme 
1  Decagramme 
1  Hectogramme 
1  Kilogramme 


GRAINS. 

0.01543 

0.15432 

1.54323 

15.43234 

154.32349 

1543.23488 

15432.34880 


OUNCES  TROT 
=  480  GRAINS. 

0.000032 
0.000321 
0.003215 
0.032150 
0.321507 
3.215072 
32.150726 

POUNDS 
AVOIRDUPOIS. 

0.0000022 
0.0000220 
0.0002204 
0.0022046 
0.0220462 
0.2204621 
2.2046212 

1  Grain  =    0.064799  grammes. 

1  Oz.  Troy  =  31.103496        " 

1  Lb.  Avoirdupois  =    0.453495  kilogrammes. 

1  Cubic  Centimetre  of  water  weighs  1  gramme. 


To  convert  Centigrade  degrees  into  Fahrenheit  degrees,  multiply  by  9  and 
divide  by  5 ;  add  32°. 

To  convert  Fahrenheit  degrees  into  Centigrade  degrees,  subtract  32°,  then 
multiply  by  5  and  divide  by  9. 


1  Metre          =  39.370708  inches. 
1  Centimetre  =    0.39370        " 
1  Millimetre  =   0.03937        " 


llnch 


=   2.539954  centimetres. 


677 


INDEX. 


Acetamide,  505. 
Acetates,  495. 
Acetic  anhydride,  499. 
Acetone,  503. 
Acetones,  420. 
Acetonitrile,  449. 
Acetyl  chloride,  502. 
Acetylene,  520. 
Acid,  42. 

acetic,  492. 

aconitic,  559. 

acrylic,  512. 

alloxanic,  561. 

amidacetic,  544. 

/3-amidopropionic,  546. 

anisic,  631. 

anthranilic,  634. 

antimonic,  189. 

arsenic,  182. 

arsenious,  179. 

aspartic,  554. 

benzole,  626. 

boric,  193. 

bromic,  130. 

butyric,  508. 

campholic,  601. 

camphoric,  602. 

caproic,  510. 

carbonic,  206,  209. 

cerotic,  511. 

chlorethylsulphurous,  528. 

chloric,  125. 

chlorous,  123. 

cholalic,  672. 

chromic,  347. 

cinchonic,  654. 

citraconic,  559. 

citric,  558. 

crotonic,  512. 

cyanic,  438. 

cyan  uric,  442. 

dialuric,  562. 

dibromosuccinic,  551. 

digallic,  590. 


Acid,  elaidic,  512. 

ethylnitrolic,  467. 
ethylphosphinic,  485. 
ethylsulphuric,  468. 
formic,  490. 
fumaric,  553. 
gallic,  632. 
gluconic,  570. 
glutamic,  659. 
glyceric,  543. 
glycocholic,  672. 
glycollic,  537. 
glyoxylic,  538. 
hippuric,  627. 
hydracrylic,  543. 
hydriodic,  132. 
hydrobromic,  128. 
hydrochloric,  116. 
hydrocyanic,  431. 
hydrofluoric,  136. 
hydrofluosilicic,  198. 
hydrosulphurous,  100. 
hypobromous,  129. 
hypochlorous,  122. 
hypophosphorous,  171. 
hyposulphuric,  109. 
hyposulphurous,  109. 
iodic,  134. 
iodopropionic,  508. 
isethionic,  528. 
isobutyric,  509. 
isophthalic,  638. 
itaconic,  559. 
lactic,  539. 
leucic,  546. 
maleic,  553. 
malic,  552. 
malonic,  536. 
manganic,  343. 
margaric,  511. 
meconic,  646. 
mellic,  593. 
mesoxalic,  561. 
metaphosphoric,  175. 

679 


680 


ELEMENTS   OF   MODERN   CHEMISTRY. 


Acid,  methylnitrolic,  451. 
monobromosuccinic,  551. 
monochloracetic,  498. 
nitric,  157. 

nitrohydrochloric,  160. 
oleic,  512. 
opianic,  650. 
oxalic,  547. 
oxamic,  550. 
oxybenzoic,  631. 
palmitic,  511. 
parabanic,  562. 
paralactic,  539,  541. 
paratartaric,  558. 
paroxybenzoic,  631. 
pentathionic,  97. 
perbromic,  130. 
perchloric,  125. 
perchromic,  87. 
periodic,  135. 
permanganic,  344. 
persulphuric,  110. 
phosphoric,  173. 
phosphorous,  172. 
phthalic,  637. 
picramic,  607. 
picric,  607. 
propionic,  507. 
purpuric,  563. 
pyrogallic,  633. 
pyrophosphoric,  174. 
pyrotartaric,  555. 
pyruvic,  555. 
quinic,  651. 
quinolic,  653. 
ruberythric,  642. 
salicylic,  629. 
silicic,  199. 
stannic,  354. 
stearic,  511. 
succinic,  550. 
sulphocarbonic,  215. 
sulphosulphuric,  109. 
sulphuric,  102. 

"         fuming,  108. 
sulphurous,  97. 
tannic,  589. 
tartaric,  554. 
tartronic,  556. 
taurocholic,  672. 
terephthalic,  638. 
tetrathionic,  97. 
trichloracetic,  499. 
trithionic,  97. 
uric,  559,  675. 


Acid,  valeric,  510. 
Acids,  diatomic,  428. 

fatty,  488,  505. 

monatomic,  418. 

polyatomic,  536. 
Aconitine,  655. 
Acrolein,  512. 
Affinity,  11. 
Air,  63. 
Alanine,  545. 
Albumen,  660. 
Albuminoid  matters,  657. 
Alcohol  radicals,  425. 
Alcohol,  allyl,  478. 

ainyl,  475. 

benzyl,  623. 

butyl,  474. 

cetyl,  477. 

ethyl,  455. 

heptyl,  477. 

hexyl,  477. 

methyl,  447. 

octyl,  477. 

propyl,  474. 
Alcohols,  diatomic,  427,  521. 

monatomic,  417,  444,  472. 

polyatomic,  429,  564. 

primary,    secondary,   tertiary, 

472. 
Aldehyde,  acetic,  505. 

anisic,  631. 

benzoic,  624. 

butyric,  509. 

crotonic,  512. 

formic,  492. 

salicylic,  628. 
Aldehydes,  420. 
Aldol,  501. 
Alizarin,  641. 
Alkaloids,  643. 
Allantoin,  563. 
Alloxan,  561. 
Alloxantin,  562. 
Alloys,  236. 
Allyl  alcohol,  478. 

bromide,  518. 

iodide,  478. 

sulphide,  478. 

sulphocyanate,  478. 
Alum,  315. 
Aluminium,  313. 

chloride,  314. 

oxide,  314. 

silicates,  317. 

sulphate,  316» 


INDEX. 


681 


Amalgams,  236. 
Amides,  421. 
Amines,  422,  479. 
Ammonia,  139. 

action  of  Cl  and  I,  143. 

action  of  potassium,  145. 
Ammonium  amalgam,  145. 

carbonate,  148. 

chloride,  146. 

cyanate,  440. 

formate,  491. 

nitrate,  148. 

oxalate,  549. 

sulphate,  149. 

sulphide,  147. 

sulphoeyanate,  444. 

sulphydrate,  147. 

theory  of,  146. 
Amygdalin,  587. 
Auiyl  alcohols,  475. 

chloride,  476. 

iodide.  476. 

oxide,  476. 
Ainyk-nes,  519. 

bromides,  520. 
Anilides,  609. 
Aniline,  608. 

colors,  613. 

salts,  608. 

Anisic  compounds,  631. 
Anthracene,  640. 
Anthracite,  202. 
Anthraquinone,  641. 
Antimonio-potassiutn  tartrate,  557. 
Antimony,  185. 

antimonate,  188. 

oxide,  188. 

pentachloride,  187. 

pentasulphide,  190. 

pentoxide,  189. 

trichloride,  186. 

trisulphide,  189. 
Apomorphine,  648. 
Aromatic  compounds,  590. 
Arsenic,  176. 

chloride,  179. 

disulphide,  183. 

pentasulphide,  184. 

pontoxide,  182. 

trioxide,  179. 

trisulphide,  183. 
Arsines,  423. 
Asparagin,  553. 
Atomic  heats,  34. 
Atomic  theory,  27. 

2D* 


Atomicity,  theory  of,  222. 
Atropine,  656. 
Aurin,  608. 
Australine,  598. 
Azobenzol,  604. 
Azoxybenzol,  604 

Barium,  302. 

carbonate,  304. 

chloride,  303. 

dioxide,  302. 

nitrate,  303. 

oxide,  302. 

sulphate,  304. 

sulphide,  303. 

tests,  304. 
Beer,  579. 
Benzamide,  627. 
Benzol,  602. 

monobromo-,  603. 

monochloro-,  603. 
Benzoyl  hydride,  624. 

chloride,  625. 
Benzyl  alcohol,  623. 

aldehyde,  624. 

chloride,  620. 
Benzylamine,  624. 
Berthollet's  laws,  265. 
Bilirubin,  673. 
Biliverdin,  673. 
Bismuth,  349. 

chloride,  350. 

nitrate,  351. 

oxide,  350. 

tests,  351. 

Bituminous  coal,  202. 
Borneol,  602. 
Boron,  191. 

chloride,  192. 

fluoride,  193. 

oxide,  193. 

Boro-potassium  tartrate,  558. 
Bromine,  127. 
Brucine,  654. 
Bunsen  burner,  221. 
Butane,  455. 
Butyl  alcohols,  474. 
Butylenes,  518. 
Butyral,  509. 
Butyrone,  509. 

Cacodyl,  453. 
Cadmium,  337. 

iodide,  337. 

oxide,  337. 


682 


ELEMENTS   OF   MODERN   CHEMISTRY. 


Cadmium,  sulphate,  338. 

sulphide,  337. 
Caesium,  300. 
Caffeine,  657. 
Calcium,  305. 

carbonate,  307. 

chloride,  307. 

hydrate,  305. 

hypochlorite,  309. 

lactate,  542. 

nitrate,  307. 

oxide,  305. 

sulphate,  308. 

tests,  310. 
Camphenes,  599. 
Camphor,  600. 

artificial,  591'. 
Carbamide,  440. 
Carbon,  200. 

dioxide,  209. 

disulphide,  215. 

estimation  of,  406. 

monoxide,  207. 

compounds  of,  438. 

oxysulphule,  216. 

tetrachoride,  449. 

sesquichloride,  516. 
Carbonates,  275. 
Carbonyl  chloride,  208. 
Carbylamines,  450,  465. 
Casein,  667. 
Cellulose,  584. 
Charcoal,  202. 

absorbent  properties  of,  204. 
Chloral,  502. 
Chlorides,  246. 

monatomic,  415. 

of  acid  radicals,  421. 
Chlorine,  112. 

and  Br  and  I,  analogies,  136. 

peroxide,  124. 
Chloroform,  448. 
Chlorotoluols,  620. 
Chlorous  anhydride,  123. 
Cholcsterin,  671. 
Chondrin,  668. 
Chromates,  347. 
Chromium,  346. 

chlorides,  348. 

oxides,  346. 
Cinchona  bark,  650. 
Cinchonine,  653. 
Citrine,  600. 
Cobalt,  338. 

chloride,  339. 


Cobalt,  oxides,  338. 

sulphate,  339. 

tests,  339. 
Cocaine,  655. 
Codeine,  648. 

Combination,  laws  of,  23-27. 
Combustion,  58. 
Conine,  644. 
Copper,  368. 

acetates,  496. 

alloys,  375. 

carbonates,  374. 

chlorides,  372. 

oxides,  371. 

sulphates,  373. 

sulphides,  372. 

tests,  375. 
Cotarnine,  650. 
Creatine,  674. 
Creatinine,  675. 
Cresols,  621. 
Cupellation,  359,  389. 
Cyanobenzol,  605. 
Cyanogen,  430. 

bromide,  437. 

chlorides,  436. 

iodide,  437. 
Cymene,  599. 

Dextrin,  581. 
Diamines,  428. 
Diamond,  201. 
Diazoamidobenzol,  612. 
Diazobenzol  compounds,  610. 
Dichlorhydrin,  531. 
Dimethylarsinc,  453. 
Dioxindol,  636. 
Diphenylamine,  614. 
Diphenylketone,  627. 
Ductility,  233. 
Dulcite,  566. 

Elementary  analysis,  406. 
Elements,  table  of,  39. 
Emulsin,  587. 
Epichlorhydrin,  531. 
Erythrite,  565. 
Ethane,  455. 
Ether,  459. 

acetylacetic,  498. 

Kay's,  449. 
Ethers  compound,  41 9. 

simple,  454. 
Ethyl  acetate,  497. 

carbamate,  470. 


INDEX. 


683 


Ethyl  carbonate,  469. 

carbylamine,  465. 

chloride,  463. 

chlorocarbonate,  470. 

cyanate,  468. 

cyanide,  465. 

hydrate,  455. 

iodide,  464. 

nitrate,  467. 

nitrite,  466. 

oxalate,  549. 

oxide,  459. 

sulphate,  469. 

sulphide,  463. 

sulphydrate,  462. 
Ethylamines,  482. 
Ethylene,  513. 

acetates,  525. 

bromide,  515. 

chlorhydrate,  524. 

chloride,  515. 

chloro-derivatives,  515. 

diamines,  527. 

hydrate,  523. 

iodide,  515. 

nitrates,  525. 

oxide,  525. 

bases  from,  526. 
Ethylhydrazine,  480. 
Ethylidene  chloride,  501,  516. 
Ethylphosphines,  483. 

Fats,  natural,  532. 
Fermentation,  576. 
Ferric  chloride,  327. 

oxide,  326. 

sulphate,  329. 

Ferro-potassium  tartrate,  557. 
Ferrous  chloride,  327. 

lactate,  542. 

oxide,  325. 

sulphate,  328. 
Fibrin,  662. 
Flame,  218. 
Fluorescein,  638. 
Fluorine,  136. 
Formates,  491. 
Formonitrile,  432. 
Formulae,  constitutional,  empirical, 

rational,  419. 
Fulminates,  452. 
Functions,  organic,  414. 

Gallium,  335. 
Gay-Lussac's  law,  27. 


Gelatin,  667. 
Gilding,  394. 
Globulin,  667. 
Glucosan,  568. 
Glucose,  567. 
Glucosides,  586. 
Glycerin,  529. 

ethers  of,  530. 
Glycocol,  544. 
Glycogen,  583. 
Glycol,  523. 

ethers  of,  427. 
Glycol?,  427,  521. 
Glyoxal,  538. 
Gold,  391.  * 

assay,  395. 

chlorides,  393. 

oxides,  393. 
Graphite,  201. 
Guanine,  676. 
Gum  arable,  584. 

tragacanth,  584. 
Gums,  583. 
Gun-cotton,  586. 

Hematin,  666. 
Hemoglobin,  664. 
Hexamethylbenzol,  619. 
Homologous  bodies,  405. 
Hydrazine,  480. 
Hydrazo benzol,  604. 
Hydrocarbons,  CnH2n+2,  415,  470. 

CnH*n,  517. 

OH2n-2,  520. 
Hydrogen,  48. 

absorption  by  palladium,  51. 

antimonide,  186. 

arsenide,  178. 

dioxide,  85. 

estimation  of,  406. 

persulphide,  96. 

phosphide,  165. 

silicide,  195. 

sulphide,  92. 
Hydroquinone,  616. 
Hydroxylamine,  149. 
Hypochlorous  anhydride,  122. 
Hypoxanthine,  676. 

Indigo,  633. 

white,  634. 
Indium,  336. 
Indol,  636. 
Inosite,  571. 
Inulin,  583. 


684 


ELEMENTS   OF   MODERN   CHEMISTRY. 


Iodine,  130. 

oxides,  134. 
Iron,  318. 

carbonate,  329. 

cast,  323. 

chlorides,  327. 

lactate,  542. 

oxides,  325. 

soft,  322. 

sulphates,  328. 

sulphides,  327. 

tests,  330. 
Isatin,  635. 
Isomerism,  412. 
Isomorphism,  37,  255. 
Isopropjl  iodide,  474. 
Isoturpentine,  600. 

Kay's  ether,  449. 

Lactamide,  542. 
Lactates,  542. 
Lactose,  574. 
Lamp-black,  203. 
Lead,  357. 

acetates,  496. 

carbonate,  366. 

chloride,  364. 

chromate,  367. 

dioxide,  362. 

iodide,  364. 

monoxide,  361. 

nitrate,  365. 

red  oxide,  362. 

sulphate,  365. 

sulphide,  363. 

tests,  367. 
Lecithine,  670. 
Leucanilines,  612. 
Leucine,  546,  675. 
Levulosan,  570. 
Levulose,  570. 
Lignite,  202. 
Lime,  305. 
Lithium,  299. 

Magnesium,  310. 

carbonate,  312. 

citrate,  559. 

chloride,  311. 

oxide,  311. 

sulphate,  312. 

tests,  313. 
Malleability,  233. 
Maltose,  575. 


Manganese,  342. 

carbonate,  345. 

dioxide,  342. 

oxides,  342. 

sulphate,  344. 

tests,  345. 
Mannitan,  566. 
Mannite,  566. 
Marsh's  apparatus,  181. 
Marsh  gas,  445. 
Matches,  165. 
Mercur-ethyl,  486. 
Mercuric  chloride,  380. 

iodide,  381. 
Mercur-methyl,  486. 
Mercurous  chloride,  379. 

iodide,  381. 
Mercury,  375. 

cyanide,  433. 

fulminate,  452. 

nitrates,  382. 

oxides,  378. 

sulphates,  383. 

sulphide,  378. 

tests,  383. 
Mesitylene,  505. 
Metal dehyde,  501. 
Metallic  carbonates,  275. 

chlorides,  246. 

hydrates,  244. 

nitrates,  271. 

oxides,  238. 

sulphates,  273. 

sulphides,  245. 
Metals,  classification  of,  277. 

general  properties  of,  231. 
Metamerism,  412. 
Methane,  445. 
Methylamines,  481. 
Methylbenzol,  618. 
Methyl  bromide,  448. 

chloride,  448. 

compounds,  445. 

cyanide,  449. 

hydrate,  447. 

iodide,  448. 

nitrate,  450. 

nitrite,  450. 

oxide,  447. 

salicylate,  630. 
Mineral  waters,  82. 
Minium,  362. 
Molecular   weights,    determination 

of,  410. 
Monobromobenzol,  603. 


INDEX. 


685 


Monochlorobenzol,  603. 
Monochlorhydrin,  531. 
Morphine,  647. 
Murexide,  563. 
Myosin,  663. 

Naphthalene,  639. 
Naphthol,  640. 
Naphthylamine,  640. 
Narceine,  646. 
Narcotine,  649. 
Neurine,  527,  671. 
Nickel,  340. 

chloride,  341. 

oxides,  340. 

sulphate,  341. 

tests,  341. 
Nicotine,  645. 
Nitrates,  271. 
Nitrethane,  466. 
Nitric  anhydride,  157. 
Nitrobenzol,  604. 
Nitroferrocyanides,  436. 
Nitrogen,  138. 

chloride,  144. 

dioxide,  153. 

estimation  of,  406. 

group,  gen.  considerations,  190. 

iodide,  145. 

monoxide,  151. 

pentoxide,  157. 

peroxide,  155. 

trioxide,  154. 
Nitroglycerin,  530. 
Nitromethane,  450. 
Nitrosyl  chloride,  161. 
Nitrotoluols,  620. 
Nitryl,  chloride  and  bromide,  156. 
Nomenclature,  37. 
Nornarcotine,  650. 
Notation,  37. 

Oils,  essential,  596. 

fatty  and  drying,  533. 
Olein,  533. 
Opium,  646. 
Orcin,  486,  621. 

Organo-metallic  compounds,  423. 
Orpiment,  183. 
Oxalates,  548. 
Oxamide,  549. 
Oxindol,  636. 
Oxygen,  54. 
Oxyphenols,  614. 
Ozone,  59. 


Palmitine,  533. 
Papaverine,  646. 
Paraconine,  645. 
Paraldehyde,  501. 
Persulphuric  oxide,  110. 
Phenanthrene,  641. 
Phenol,  605. 
Phloretin,  589. 
Phloridzin,  588. 
Phloroglucin,  589,  618. 
Phosphines,  423. 
Phosphoric  anhydride,  173. 
Phosphorus,  161. 

bromide,  169. 

iodide,  170. 

oxychloride,  169. 

pentachloride,  168. 

pentoxide,  173. 

sulphides,  176. 

sulphochloride,  159. 

trichloride,  168. 
Pinacolin,  505. 
Pinacone,  522. 
Platinum,  395. 

chlorides,  397. 
Plumbago,  201. 
Polymerism,  412. 
Populin,  588. 
Potassamide,  145. 
Potassium,  282. 

acetate,  495. 

acid-sulphate,  288. 

bromide,  286. 

carbonates,  289. 

chlorate,  288. 

chloride,  285. 

chromate,  347. 

cyanate,  439. 

cyanide,  433. 

dichromate,  347. 

ferricyanide,  435. 

ferrocyanide,  434. 

hydrate,  283. 

iodide,  285. 

methylate,  447. 

nitrate,  286. 

oxalates,  549. 

oxides,  283. 

perchl orate,  289. 

permanganate,  344. 

sulphate,  288. 

sulphides,  284. 

sulphocyanate,  444. 

tartrates,  556. 

tests,  290. 


58 


686 


ELEMENTS    OF   MODERN    CHEMISTRY. 


Pottery,  317. 
Propionitrile,  465. 
Propyl  alcohols,  474. 

glycols,  529. 

iodide,  474. 
Propylene,  518. 
Prussian  blue,  435. 
Pseudoinorphine,  647. 
Purpurin,  643. 
Pyrocatechin,  615. 
Pyrogallol,  618. 

Quinine,  651. 
Quinone,  616. 

Radicals,  monatomic,  425. 

polyatomic,  426. 
Realgar,  183. 
Resorcin,  615. 
Respiration,  669. 
Richter's  laws,  253. 
Rochelle  salt,  556. 
Rosaniline,  611. 
Rubidium,  300. 

Saccharose,  571. 
Safety-lamp,  219. 
Salicin,  588. 
Salicyl  hydride,  628. 
Saligenin,  588,  628. 
Salts,  43,  250. 

action  of  acids,  265. 
bases,  267. 
electricity,  262. 
heat,  261. 
metals,  264. 
salts,  268,  270. 
water,  256. 

neutral,  acid,  and  basic,  252. 
Saponifieation,  535. 
Sarcine,  676. 
Sarcosine,  674. 
Selenium,  111. 
Silica,  199. 
Silicon,  194. 

chloride,  196. 

fluoride,  197. 

oxide,  199. 
Silver,  384. 

acetate,  497. 

assay,  389. 

chloride,  387. 

fulminate,  452. 

fulminating,  387. 

iodide,  388. 


Silver,  nitrate,  388. 

oxide,  387. 

sulphide,  387. 

tests,  389. 
Silvering,  389. 
Soap,  534. 
Sodium,  291. 

acetate,  496. 

acid-carbonate,  298. 

acid-sulphate,  295. 

borate,  298. 

carbonate,  295. 

chloride,  293. 

hydrate,  292. 

hydrosulphite,  100. 

hyposulphite,  109. 

nitroferrocyanide,  436. 

oxides,  292. 

phosphates,  298. 

sulphate,  294. 

sulphide,  292. 

tests,  299. 
Sorbin,  571. 
Sorbite,  567. 
Specific  heat,  34. 
Spectrum  analysis,  300. 
Stannethyls,  487. 
Starch,  580. 
Stearin,  533. 
Stearin  candles,  534. 
Steel,  323. 
Stibines,  423. 
Strontium,  304. 
Strychnine,  654. 
Succinic  anhydride,  551. 
Succinyl  chloride,  551. 
Sugar,  cane,  571. 

grape,  567. 

inverted,  574. 

milk,  574. 
Sugars,  567. 
Sulphates,  273. 
Sulphur,  88. 

chlorides,  126. 

soft,  90. 

Sulphuric  anhydride,  101. 
Sulphurous  anhydride,  97. 
Sulphuryl  chloride,  100,  106. 
Supersaturation,  259. 
Syntonin,  664. 

Tannin,  589. 
Tartar-emetic,  557. 
Tartrates,  556. 
Taurine,  528. 


INDEX. 


687 


Tellurium,  111. 
Terebene,  599. 
Terpileno,  600. 
Terpin,  598. 

Tetrachlorethylene,  516. 
Tetramethylammonium,  482. 
Tetrethylainmonium,  483. 
Thallium,  302. 
Thebaine,  646. 
Theine,  657. 
Theobromine,  656. 
Tin,  352. 

dichloride,  355. 

oxides,  354. 

sulphides,  355. 

tests,  357. 

tetrachloride,  356. 
Toluidines,  622. 
Toluol,  618. 
Tribenzylamine,  624. 
Trichlorhydrin,  532. 
Triethylamine,  483. 
Trimethylamine,  482. 
Trimethylcarbinol,  475. 
Trinitrophenol,  607. 
Turpentine,  596,  598. 
Tyrosine,  631. 

Urea,  440. 

Ureas,  compound,  443. 


Urethane,  470. 

Verdigris,  497. 
Vermillion,  379. 
Vinegar,  494. 

Water,  70. 

analysis,  71. 

mineral,  82. 

natural  state,  79. 

synthesis,  72. 
Wax,  477. 
Wine,  578. 
Wood-spirit,  447. 

Xanthine,  675. 
Xyloidin,  582. 
Xylols,  637. 

Yeast,  576. 

Zinc,  330. 

chloride,  333. 

hydracrylate,  543. 

lactate,  542. 

oxide,  332. 

sulphate,  333. 

sulphide,  333. 

tests,  334. 
Zinc-ethyl,  486. 


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they  wrote;  to  give,  wherever  possible,  some  connected  outline 
of  the  story  which  they  tell,  or  the  facts  which  they  record,  checked 
by  the  results  of  modern  investigations ;  to  present  some  of  their 
most  striking  passages  in  approved  English  translations,  and  to 
illustrate  them  generally  from  modern  writers ;  to  serve,  in  short, 
as  a  popular  retrospect  of  the  chief  literature  of  Greece  and  Rome. 


*'  Each  successive  issue  only  adds  to 
our  appreciation  of  the  learning  and 
skill  with  which  this  admirable  enter- 
prise of  bringing  the  best  classics  within 
easy  reach  of  English  readers  is  con- 
ducted."—New  York  Independent. 

***  A  Supplemental  Series  in  the  same  size  and  type  i 
issued.     It  will  not  be  extended  beyond  eight  or  ten  volumes 


"  There  is  not  a  volume  of  this  most 
admirable  and  useful  series  that  is  not 
done  in  a  very  masterly  mannrr,  and 
worthy  of  the  highest  praise." — Pritisk 
Quarterly  Review. 


PUBLICATIONS  OF  J.  B.  LIPPINCOTT  &  CO. 


VALUABLE  WORKS  OF  REFERENCE. 


Lippincott's  Pronouncing  Biographical  Dictionary. 

Containing  complete  and  concise  Biographical  Sketches  of  the 
Eminent  Persons  of  all  Ages  and  Countries.  By  J.  THOMAS, 
A.M.,  M.D.  Imperial  8vo.  Sheep.  $15,00.  2  vois.  Cloth. 
$22.00. 

Allibone's  Critical  Dictionary  of  Authors. 

A  Dictionary  of  English  Literature  and  British  and  American 
Authors,  Living  and  Deceased.  By  S.  AUSTIN  ALLIBONE,  LL.D. 
3  vols.  Imperial  Svo.  Extra  cloth.  $22.50. 

Lippincott's  Pronouncing  Gazetteer  of  the  World. 

A  Complete  Geographical  Dictionary.  By  J.  THOMAS  and 
T.  BALDWIN.  Royal  Svo.  Sheep.  $10.00. 

Allibone's  Dictionary  of  Prose  Quotations. 

By  S.  AUSTIN  ALLIBONE,  LL.D.  With  Indexes.  Svo.  Extra 
cloth.  $5.00. 

Allibone's  Dictionary  of  Poetical  Quotations. 

By  S.  AUSTIN  ALLIBONE,  LL.D.  With  Indexes.  Svo.  Extra 
cloth.  $5.00. 

Chambers's  Encyclopaedia. 

American  Bevised  Edition. 

A  Dictionary  of  Useful  Knowledge.  Profusely  Illustrated  with 
Maps,  Plates,  and  Woodcuts.  10  vols.  Royal  Svo. 

Chambers's  Book  of  Days. 

A  Miscellany  of  Popular  Antiquities  connected  with  the  Cal- 
endar. Profusely  Illustrated.  2  vols.  Svo.  Extra  cloth.  $8.00. 

Dictionary  of  Quotations, 

From  the  Greek,  Latin,  and  Modern  Languages.  With  an 
Index.  Crown  Svo.  Extra  cloth.  $2.00. 

Furness's  Concordance  to  Shakespeare's  Poems. 

An  Index  to  Every  Word  therein  contained,  with  the  Complete 
Poems  of  Shakespeare.  Svo.  Extra  cloth.  $4.00. 

Lempriere's  Classical  Dictionary. 

Containing  all  the  Principal  Names  and  Terms  relating  to 
Antiquity  and  the  Ancients,  with  a  Chronological  Table.  Svo. 
Sheep.  $3.75.  i6mo.  Cloth.  $1.50. 


4®=-  The  above  Works  are  also  bound  in  a  variety  of  handsome  extra  styles 


PUBLICATIONS  OF  J.  B.  LIPPINCOTT  &  CO. 

CLASSICAL  WORKS  OF  REFERENCE. 

GARDNER'S  LATIN  LEXICON. 

A  Dictionary  of  the  Latin  Language,  particularly  adapted  to  the 
Classics  usually  studied  preparatory  to  a  Collegiate  Course.  By 
FRANCIS  GARDNER,  A.M.  8vo.  Sheep.  $3.00. 

LEVERETTS  LATIN  LEXICON. 

A  Copious  Lexicon  of  the  Latin  Language.  Compiled  chiefly  from 
the  Magnum  Totius  Latinitatis  Lexicon  of  Facciolati  and  For- 
cellini,  and  the  German  Works  of  Scheller  and  Luenemann, 
embracing  the  Classical  Distinctions  of  Words,  and  the  Etymo- 
logical Index  of  Freund's  Lexicon.  By  F.  P.  LEVERETT.  Large 
8vo.  Sheep.  $5.50.* 

This  work  contains  all  the  words  in  the  Latin  language,  embracing  those  used 
by  authors  of  the  classical,  ante-classical,  and  post-classical  periods,  with  words 
M  modern  origin  coined  for  scientific  and  other  purposes. 

LEMPRIERE'S  CLASSICAL  DICTIONARY. 

Containing  a  full  account  of  all  the  Proper  Names  mentioned  in 
ancient  authors,  with  Tables  of  Coins,  Weights,  and  Measures 
in  use  among  the  Greeks  and  Romans ;  to  which  is  prefixed  a 
Chronological  Table.  8vo.  Sheep.  $3.25.*  ABRIDGED  EDI- 
TION. I2mo.  Extra  cloth.  $1.50. 

The  original  text  of  Lempriere  has  in  this  edition  been  carefully  revised  and 
amended,  and  much  valuable  original  matter  added.  The  work  is  now  a  complete 
Bibliotheca  Classica,  containing  in  a  condensed  and  readily  accessible  form  all  the 
information  required  by  the  student  upon  the  geography,  topography,  history,  lit- 
enture,  and  mythology  of  antiquity  and  of  the  ancients,  with  bibliographical  ref- 
c»*nces  for  such  as  wish  to  get  fuller  information  on  the  subjects  treated  of. 

GROVES'S  GREEK  DICTIONARY. 

A  Greek  and  English  Dictionary,  comprising  all  the  Words  in  the 
writings  of  the  most  popular  Greek  authors,  with  the  difficult 
inflections  in  them,  and  in  the  Septuagint  and  New  Testament. 
Designed  for  the  Use  of  Schools  and  the  Under-Graduate  Course 
of  a  Collegiate  Education.  By  JOHN  GROVES.  With  correc- 
tions and  additional  matter  by  the  American  editor.  8vo. 
Sheep.  $2.25.* 

The  object  of  the  compiler  has  been  to  produce  a  work  which  young  Greek 
scholars  could  use  with  ease  and  advantage  to  themselves,  but  sufficiently  full  to 
be  equally  serviceable  as  they  advanced. 

PICKERING'S  GREEK  LEXICON. 

A  Comprehensive  Lexicon  of  the  Greek  Language,  adapted  to  the 
Use  of  Colleges  and  Schools  of  the  United  States.  By  JOHN 
PICKERING,  LL.D.  New  Edition,  revised  and  corrected.  Large 
8vo.  Sheep.  $5.50.* 

This  work  contains  all  the  words  in  the  Greek  language,  with  their  correct  inter- 
pretation into  English,  and  their  different  shades  of  meaning  carefully  distinguished 
and  illustrated  by  citations  from  standard  authors. 


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16  J933 
FEB  24  W38 


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IN  STACKS 

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t     BEC'D  ID  J 


LD  21-50m-l,'83 


YC  22066 


